JP2018104819A - Nickel powder and manufacturing method therefor, and surface treatment method of nickel powder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nickel powder capable of exhibiting resin degradation inhibition in a nickel paste dried film by conventional sulfur addition with less amount of tin addition amount or sinter behavior improvement of the nickel powder, a manufacturing method of the nickel powder by a wet method capable of simply and easily manufacturing the nickel powder, and a surface treatment method of the nickel powder.SOLUTION: There is provided a nickel powder, which has a particle shape with an almost spherical shape and average particle diameter of 0.03 μm to 0.5 μm, and is surface-treated with tin, in which content of tin is less than 1.5 mass%. The nickel powder is manufactured by adding an alkali-soluble tin salt or an acid-soluble tin salt to a nickel powder slurry in which nickel particles are dispersed in a dispersion so that tin addition amount to nickel in the finally obtained nickel powder surface-treated with tin is less than 1.5 mass%, mixing them, reducing the alkali-soluble tin salt or the acid-soluble tin salt and modifying the nickel powder surface with tin.SELECTED DRAWING: Figure 5

Description

  The present invention relates to a high-performance nickel powder used as an electrode material of a multilayer ceramic component and a method for producing the same, and a surface treatment method for the nickel powder, and in particular, an inexpensive and high-performance nickel powder obtained by a wet method and a method for producing the same. And a surface treatment method of nickel powder.

  Nickel powder is used as a material for capacitors of electronic circuits, particularly as a material for thick film conductors constituting internal electrodes of multilayer ceramic components such as multilayer ceramic capacitors (MLCC) and multilayer ceramic substrates. Yes.

  In recent years, the capacity of monolithic ceramic capacitors has increased, and the amount of internal electrode paste used to form the internal electrodes of monolithic ceramic capacitors has also increased significantly. For this reason, inexpensive base metals such as nickel are mainly used instead of expensive noble metals as the metal powder for the internal electrode paste constituting the thick film conductor.

  In the process of manufacturing a multilayer ceramic capacitor, an internal electrode paste kneaded with nickel powder, a binder resin such as ethyl cellulose, and an organic solvent such as terpineol is screen-printed on a dielectric green sheet. The dielectric green sheet on which the internal electrode paste is printed and dried is laminated so that the internal electrode paste printed layers and the dielectric green sheets are alternately overlapped, and further pressed to obtain a laminate.

  The laminated body is cut into a predetermined size, then the binder resin is removed by heat treatment (debinding treatment), and the laminated body is fired at a high temperature of about 1300 ° C., thereby forming a ceramic molded body. Is obtained.

  And an external electrode is attached to the obtained ceramic molded body, and a multilayer ceramic capacitor is obtained. Since a base metal such as nickel is used as the metal powder in the internal electrode paste that becomes the internal electrode, the debinding treatment of the laminate has an extremely high oxygen concentration such as an inert atmosphere so that these base metals are not oxidized. Performed in a low atmosphere.

  With the miniaturization and large capacity of multilayer ceramic capacitors, both internal electrodes and dielectrics are being made thinner. Along with this, the particle size of the nickel powder used for the internal electrode paste is also made finer, and a nickel powder having an average particle size of 0.5 μm or less is required, especially a nickel powder having an average particle size of 0.3 μm or less. The use of is becoming mainstream.

  The production method of nickel powder is roughly classified into a vapor phase method and a wet method. Examples of the gas phase method include a method of producing nickel powder by reducing nickel chloride vapor described in Patent Document 1 with hydrogen, or vaporizing nickel metal described in Patent Document 2 in plasma. There is a method for producing nickel powder. As a wet method, for example, there is a method described in Patent Document 3 in which a reducing agent is added to a nickel salt solution to produce nickel powder.

  The vapor phase method is an effective means for obtaining high-quality nickel powder having excellent crystallinity due to a high-temperature process of about 1000 ° C. or higher, but has a problem that the particle size distribution of the obtained nickel powder becomes wide. . As described above, the thinning of the internal electrode requires a nickel powder having an average particle size of 0.5 μm or less that does not include coarse particles and has a relatively narrow particle size distribution. In order to obtain nickel powder, classification treatment by introducing an expensive classification device is essential.

  In the classification process, coarse particles larger than the classification point can be removed with a classification point having an arbitrary value of about 0.6 μm to 2 μm, but part of particles smaller than the classification point are also removed at the same time. Therefore, there is a problem that the actual product yield is greatly reduced. Therefore, the gas phase method inevitably increases the cost of the product, including the introduction of the expensive equipment described above.

  Further, in the vapor phase method, when nickel powder having an average particle size of 0.2 μm or less, particularly 0.1 μm or less is used, it is difficult to remove coarse particles by classification treatment. It cannot cope with the thinning of the layer.

On the other hand, the wet method has an advantage that the particle size distribution of the obtained nickel powder is narrower than the vapor phase method. In particular, in the method of preparing nickel powder by crystallization that performs a reduction reaction in a reaction solution obtained by adding a solution containing hydrazine as a reducing agent to a solution containing a copper salt to a nickel salt described in Patent Document 3. , Because the nickel salt (exactly nickel ion (Ni ²⁺ ) or nickel complex ion) is reduced by hydrazine in the presence of a metal salt (nucleating agent) that is nobler than nickel. It is controlled (that is, the particle size is controlled), and nucleation and particle growth become uniform, and a fine nickel powder with a narrower particle size distribution (hereinafter, nickel powder generated in the reaction solution is referred to as “nickel crystallized powder”. It is known that it is sometimes obtained). For reference, a typical manufacturing process of nickel powder by a wet method is shown in FIG.

  By the way, when the nickel powder obtained by the vapor phase method or the wet method is applied to the multilayer ceramic capacitor, a nickel paste dry film containing nickel powder and a resin as the main components (drying obtained by printing and drying the nickel paste) In order to suppress resin decomposition (decomposition of resin due to resin decomposition catalysis by the active surface of nickel powder) or to bring the sintering temperature of nickel powder close to the sintering temperature of dielectric, Sulfur (S) is added when producing powder, but nickel powder produced by adding sulfur tends to lower the sintering temperature, so sulfur is removed during the production process of multilayer ceramic capacitors. It is preferable to do. However, as the specific surface area of the nickel powder increases in accordance with the recent refinement of the nickel powder, the amount of sulfur added necessary for the surface treatment of the nickel powder has increased, and the removal thereof has been a problem.

  Therefore, in Patent Document 4, in the production of nickel powder using a vapor phase method, tin (Sn) is reduced to 0 in order to suppress connected particles in which nickel particles are linearly bonded and to keep the sintering temperature high. A method for producing a nickel tin alloy powder containing 5 mass% to 60 mass% is disclosed. Patent Document 5 discloses a crystal structure in which 0.1% by mass to 10% by mass of a nonmagnetic metal element tin is dissolved in nickel having a face-centered cubic lattice (FCC) structure, and the a-axis length is extended. It is disclosed that the sintering temperature of nickel powder is increased, the aggregation is suppressed, and the high-frequency characteristics are improved by distorting.

JP-A-4-365806 Japanese translation of PCT publication No. 2002-530521 JP 2002-53904 A JP 2013-170303 A WO2014 / 080600 pamphlet

  However, if the nickel tin alloy powder or the powder in which tin is dissolved in nickel as described above is replaced with nickel powder to which conventional sulfur is added, the tin component added to the nickel powder is uniformly contained in the nickel particles. Therefore, it was necessary to increase the amount of tin added in order to exhibit the effect of tin addition. Impurities other than the nickel component should be reduced as much as possible in the nickel powder for multilayer ceramic capacitors. From this point, the suppression of resin degradation and the sintering behavior of the nickel powder by the nickel paste dry film by adding conventional sulfur There is a need for a nickel powder that can exhibit the effect of improvement more effectively with a smaller amount of tin added, a nickel powder manufacturing method that can more easily produce the nickel powder, and a nickel powder surface treatment method. It was done.

  Therefore, in the present invention, nickel powder capable of exhibiting the effect of suppressing resin decomposition due to the resin decomposition catalytic action of nickel, and the surface of nickel powder, as well as conventional sulfur addition, with a smaller amount of tin addition, and the surface of nickel powder It aims at providing the manufacturing method of the nickel powder by the processing method, especially the wet method which can produce the said nickel powder more simply and easily.

  The present inventors pay attention to the inclusion form of tin added as a substitute for sulfur in the nickel powder used in the multilayer ceramic capacitor, and replace the conventional alloying (nickel tin alloy) or solid solution of tin in nickel. If surface treatment that modifies (coats) tin on nickel particles, the amount of tin is less than when alloying or solidifying, and it is more efficient to suppress resin degradation and improve the sintering behavior of nickel powder with a nickel paste dry film. I found that I can do it. In addition, a crystallization step in a method for producing nickel powder by a wet method (at least in a water-soluble nickel salt, a salt of a metal noble than nickel, a reducing agent, and an alkaline reaction liquid in which alkali hydroxide and water are mixed, Mixing nickel powder slurry (in this case, alkaline reaction final solution containing nickel crystallized powder) and tin compound (for example, alkali-soluble tin salt), which is the reaction final solution of the step of obtaining nickel crystallized powder by reduction reaction Then, it was also found that if the tin compound is reduced, tin can be surface-treated with respect to the surface of the nickel particles very simply and easily. The present invention has been completed based on such findings.

  That is, one embodiment of the present invention has a substantially spherical particle shape, an average particle diameter of 0.03 μm to 0.5 μm, surface-treated with tin, and a tin content of 1.5 mass. It is nickel powder which is less than%.

  Resin decomposition temperature measurement in which only the ethyl cellulose resin is heated in an inert atmosphere is measured, and the resin decomposition peak temperature (Tr) which is the temperature indicating the maximum value of the mass change amount in the profile of the mass change amount with respect to the temperature; A resin decomposition temperature measurement is performed by heating the mixture of ethyl cellulose resins in an inert atmosphere, and a difference from a resin decomposition peak temperature (Tn) which is a temperature indicating a maximum value of the mass change amount in a profile of the mass change amount with respect to the temperature ( Tr-Tn) may be 40 ° C. or lower.

  The tin content may be less than 0.5% by mass.

  You may contain 0.15 mass% or less of sulfur.

  In order to solve the above problems, one embodiment of the present invention provides a nickel powder surface-treated with tin having a substantially spherical particle shape and an average particle diameter of about 0.03 μm to 0.5 μm. A surface treatment method comprising a surface treatment step with tin, the surface treatment step with tin comprising a tin compound mixing step and a tin reduction step, wherein the tin compound mixing step has a substantially spherical particle shape. A nickel powder slurry in which nickel powder having an average particle size of about 0.03 μm to 0.5 μm is dispersed in a solvent and a tin compound are mixed so that the amount of tin added to nickel is less than 1.5% by mass. The tin reduction step includes a step of reducing the tin compound during the tin compound mixing step or after the tin compound mixing step, wherein the tin compound is an alkali-soluble tin salt or an acid-soluble tin salt. There is a surface treatment method of the nickel powder.

  The tin reduction step may include a step of reducing the alkali-soluble tin salt with a reducing agent in an alkaline solution.

  The alkali-soluble tin salt may be a tin oxoacid salt.

The tin oxo acid salt is ammonium silver salt or alkali metal stannate (X ₂ SnO ₃ , where X = NH ₄ , Li, Na, K, Rb, Cs). There may be.

  The tin reduction step is a step of reducing the acid-soluble tin salt by a substitution reaction with the nickel particles in an acidic solution, or reducing the acid-soluble tin salt with the nickel particles in an acidic solution. In addition to the reaction, a step of using a reducing agent may be included.

  The acid-soluble tin salt may be at least one of a tin inorganic acid salt and a tin organic acid salt.

The tin inorganic acid salt is tin chloride (SnCl ₂ or SnCl ₄ ), tin nitrate (Sn (NO ₃ ) ₂ , or Sn (NO ₃ ) ₄ ), tin sulfate (SnSO ₄ , or Sn (SO ₄ ). ₂ ), or at least one of chlorostannic acid or a salt thereof (X ₂ SnCl ₄ or X ₂ SnCl ₆ , where X = H 2, NH ₄ , Li, Na, K, Rb, or Cs) The organic acid salt of tin may be at least one of tin methanesulfonate and tin phenolsulfonate.

  The tin reduction step may include a step of reducing the tin compound with hydrazine.

  In order to solve the above problems, one embodiment of the present invention is a nickel powder surface-treated with tin having a substantially spherical particle shape and an average particle diameter of about 0.03 μm to 0.5 μm. A manufacturing method comprising: mixing at least a water-soluble nickel salt, a salt of a metal nobler than nickel, a reducing agent, and an alkali hydroxide and water to obtain a reaction solution; A crystallization step of crystallizing nickel particles to obtain an alkaline reaction final solution containing nickel crystallization powder, and a surface treatment step with tin comprising a tin compound mixing step and a tin reduction step, and the tin compound mixing The step is a step of mixing a nickel powder slurry comprising an alkaline reaction final solution containing the nickel crystallized powder and an alkali-soluble tin salt so that the tin content relative to nickel is less than 1.5% by mass. ,Previous The tin reduction step is a method for producing nickel powder, including a step of reducing the alkali-soluble tin salt in an alkaline solution during the tin compound mixing step or after the tin compound mixing step.

  In order to solve the above problems, one embodiment of the present invention is a nickel powder surface-treated with tin having a substantially spherical particle shape and an average particle diameter of about 0.03 μm to 0.5 μm. A manufacturing method comprising at least a water-soluble nickel salt, a salt of a metal nobler than nickel, a reducing agent, and an alkali hydroxide and water to obtain an alkaline reaction solution, and then the alkaline reaction solution by a reduction reaction A surface treatment step with tin, comprising a crystallization step of crystallization of nickel particles to obtain an alkaline reaction final solution containing nickel crystallization powder, an alkali reduction step, a tin compound mixing step, and a tin reduction step The alkali reduction step is a step of obtaining a nickel powder slurry from which alkaline components have been removed or reduced from the alkaline reaction final solution, and the tin compound mixing step The nickel powder slurry from which the potash component is removed or reduced and the acid-soluble tin salt are mixed so that the content of tin with respect to nickel is less than 1.5% by mass, and the tin reduction step includes the tin compound It is a manufacturing method of nickel powder including the process of reducing the said acid-soluble tin salt during a mixing process or after the said tin compound mixing process.

  The tin reduction step may include a step of reducing the acid-soluble tin salt by a substitution reaction of nickel particles with nickel in an acidic solution.

  The tin reduction step may include a step of reducing the acid-soluble tin salt by using a reducing agent separately from the substitution reaction of the nickel particles with nickel in an acidic solution.

  The nickel powder according to the present invention is obtained by subjecting the surface of nickel particles to surface treatment with tin, unlike alloying or solid solution that uniformly adds tin into nickel particles. Therefore, the effects of suppressing the resin degradation and improving the sintering behavior of nickel powder in the dried nickel paste film by adding sulfur can be expressed more effectively with a smaller amount of tin. It is suitable for.

  Further, the surface treatment method of nickel powder according to the present invention is a method capable of surface-treating tin on the surface of nickel particles very easily and easily. Resin decomposition suppression and sintering can be performed with a smaller amount of tin. Since the effect of improving the behavior can be exhibited, a material suitable for the use of the internal electrode of the multilayer ceramic capacitor can be provided.

  Further, the nickel powder production method according to the present invention is a nickel powder slurry (alkaline containing nickel crystallized powder), which is a crystallization reaction final solution, in a crystallization process which is one step of a nickel powder production method by a wet method. This is a method in which tin can be surface-treated on the surface of nickel particles by adding and reducing a tin compound (for example, alkali-soluble stannate) to the reaction solution, and a smaller amount of tin. Therefore, high-performance nickel powder suitable for use as an internal electrode of a multilayer ceramic capacitor can be produced at low cost.

It is a schematic diagram which shows the typical manufacturing process in the manufacturing method of the nickel powder by a wet method. It is a schematic diagram which shows an example of the manufacturing process in the manufacturing method of the nickel powder of this invention. It is a schematic diagram which shows an example of the manufacturing process in the manufacturing method of the nickel powder using the wet method of this invention. It is a schematic diagram which shows another example of the manufacturing process in the manufacturing method of the nickel powder using the wet method of this invention. It is a figure which shows the result of having measured the resin decomposition | disassembly behavior of the mixed powder of nickel powder and ethylcellulose resin. 4 is a scanning electron microscope (SEM) photograph of nickel powder according to Example 3.

  Hereinafter, a nickel powder surface-treated with tin according to the present invention (hereinafter sometimes simply referred to as “nickel powder”) and a surface treatment method of the nickel powder according to the present invention with tin will be described with reference to FIG. This will be described in the following order. Further, as a preferred example of the nickel powder manufacturing method according to the present invention, a nickel powder manufacturing method using a wet method will be described in the following order with reference to FIGS. 3 and 4. It is not limited and can be arbitrarily changed without departing from the gist of the present invention.

1. 1. Nickel powder 2. Surface treatment method of nickel powder with tin 2-1. Procedure of surface treatment process with tin 2-2. Tin compound used in the surface treatment step with tin 2-3. Tin compound mixing step 2-4. 2. Tin reduction step 3. Method for producing nickel powder using wet method 3-1. Crystallization step 3-1-1. Agent used in crystallization process 3-1-2. Crystallization procedure 3-1-3. Reduction reaction 3-1-4. Reaction start temperature 3-2. Surface treatment process with tin in wet method 3-2-1. Procedure of surface treatment process with tin in wet method)
3-2-2. Tin compound used in surface treatment step with tin in wet method 3-2-3. Step of mixing tin compound in wet method 3-2-4. Tin reduction step in wet method 3-2-5. Alkali reduction step in wet method 3-3. Crushing process (post-processing process)

<1. Nickel powder>
The nickel powder of the present invention is different from alloying or solid solution, which is a uniform addition of tin into nickel particles, and is surface-treated with tin. Since the effects of suppressing decomposition and improving the sintering behavior of nickel powder can be expressed more effectively with a smaller amount of tin, it is suitable for use as an internal electrode of a multilayer ceramic capacitor.

  The nickel powder of the present invention has a substantially spherical particle shape, and the average particle diameter is 0.03 μm to 0.5 μm from the viewpoint of corresponding to the thinning of the internal electrode of the multilayer ceramic capacitor in recent years. In addition, the average particle diameter of this invention is a number average particle diameter calculated | required from the operation micrograph (SEM image) of nickel powder.

  Usually, the nickel powder may contain slight impurities. For example, the nickel powder obtained by the wet process contains oxygen, which is caused by surface oxidation of nickel particles, chlorine, which is considered to be caused by nickel chloride, which is a nickel raw material, and alkali metals, such as sodium, which is caused by sodium hydroxide. May contain trace amounts. Nickel powder obtained by the vapor phase method also contains oxygen due to the surface oxidation of nickel particles, and nickel powder obtained by hydrogen reduction of nickel chloride vapor. May be included. Since these impurities may cause defects in the internal electrodes during the production of the multilayer ceramic capacitor, it is preferable to reduce them as much as possible. For example, chlorine and alkali metals are reduced to 0 in the nickel powder. The content is preferably 0.01% by mass or less.

  Like the nickel powder of the present invention, the nickel powder applicable to the internal electrode of the multilayer ceramic capacitor usually contains a trace amount of sulfur in order to suppress its catalytic activity. This is because the surface of the nickel particles has a high catalytic activity. For example, if it is used as it is without containing sulfur or the like, the heat of the binder resin such as ethyl cellulose resin contained in the internal electrode paste in the debinding process when manufacturing the multilayer ceramic capacitor. This is because the decomposition is promoted and the binder resin is decomposed from a low temperature, the strength of the laminate is significantly reduced, and at the same time, a large amount of decomposition gas is generated and cracks are likely to occur in the laminate.

  As described above, when the surface treatment for attaching sulfur to the surface of the nickel particles is performed, the thermal decomposition of the binder resin is greatly suppressed, but as described above, the specific surface area accompanying the recent finer nickel powder is reduced. As a result of this increase, the required amount of sulfur added tends to increase. On the other hand, from the viewpoint of preventing the occurrence of internal electrode defects due to sulfur, it is preferable to remove sulfur as much as possible in the production process of the multilayer ceramic capacitor. However, when the amount of sulfur added is large, there is a problem that the removal becomes difficult. It was. Therefore, in the present invention, the tin content is less than 1.5% by mass, preferably less than 1.0% by mass, more preferably less than 0.5% by mass with respect to nickel by surface-treating tin to the nickel particles. Even if it is less, the effect of suppressing the decomposition of the binder resin is more effectively exhibited. Moreover, even when it contains sulfur, it is preferable to reduce it as much as possible. According to the surface treatment of tin on the nickel particles of the present invention, the content of sulfur is 0.15% by mass or less based on nickel. However, even when the content is preferably 0.05% by mass or less, and more preferably 0.01% by mass or less, the decomposition of the binder resin can be more effectively suppressed.

  In addition, in the surface treatment with tin according to the present invention, the tin modification (coating) state with respect to the nickel particles is thin and uniformly modified (coating) the entire nickel particles. This is most preferable from the viewpoint of reducing the influence of tin as an impurity on the characteristics of the multilayer ceramic capacitor. However, a modified (coating) state in which a part of the nickel particles is modified (coating) may be used as long as the effect of suppressing the decomposition of the binder resin can be exhibited. In the present invention, “surface treatment” is used as a concept encompassing the entire modification (coating) and partial modification (coating) of such nickel particles.

  The evaluation of the suppression of the decomposition of the binder resin of nickel powder is based on the measurement of the resin decomposition temperature in which the mixed powder of nickel powder and ethylcellulose resin powder is heated in an inert atmosphere, and the mixture of nickel powder and ethylcellulose resin is heated in an inert atmosphere. The resin decomposition temperature is measured, and the resin decomposition peak temperature (Tn) which is the temperature showing the maximum value of the mass change amount in the profile of the mass change amount with respect to the temperature, and the resin decomposition temperature at which only the ethyl cellulose resin is heated in the inert atmosphere Measurement is performed, and a resin decomposition peak temperature (Tr), which is a temperature indicating the maximum value of mass change amount in a profile of mass change amount with respect to temperature, is obtained, and then the difference (Tr-Tn) is calculated. . The larger the (Tr-Tn), the higher the surface activity of nickel, indicating that the decomposition of the ethylcellulose resin as the binder resin is promoted at a lower temperature. In the nickel powder of the present invention, (Tr-Tn) Is preferably 40 ° C. or lower. If this value exceeds 40 ° C., the strength of the laminate constituting the capacitor may be significantly reduced, or cracks may occur in the laminate.

  By increasing the content of tin with respect to the nickel powder, the value of (Tr-Tn) can be reduced (suppressing the surface activity of nickel), while tin is a low melting point metal (melting point is 232 ° C.). Because the resin decomposition peak temperature results in a molten state, if the tin content with respect to the nickel powder exceeds 1.0% by mass, the molten tin contaminates the dielectric green sheet and the capacitor characteristics of the multilayer ceramic capacitor May be reduced. The lower limit of the content of tin with respect to the nickel powder is not particularly limited. However, if the content is 0.05% by mass or more, the resin decomposition peak temperature can be increased as compared with the nickel powder before surface treatment with tin.

  As described above, when the sulfur content with respect to the nickel powder exceeds 0.15% by mass, internal electrode defects due to sulfur may occur. The lower limit of the sulfur content is not particularly limited, and may be below the detection limit with an analytical instrument used for content analysis, such as a sulfur analyzer or ICP analyzer using a combustion method.

<2. Surface treatment method of nickel powder with tin>
The surface treatment method of the nickel powder according to the present invention with tin is a surface treatment method for obtaining a nickel powder surface-treated with tin having a substantially spherical particle shape and an average particle diameter of about 0.03 μm to 0.5 μm. The surface treatment process using tin includes at least a tin compound mixing process and a tin reduction process.

  The tin compound mixing step includes a nickel powder slurry in which nickel particles having a substantially spherical particle shape and an average particle diameter of about 0.03 μm to 0.5 μm are dispersed in a solvent (finally obtained). The tin compound is added so that the amount of tin added to nickel (in the nickel powder surface-treated with tin) is less than 1.5% by mass, preferably less than 1.0% by mass, more preferably less than 0.5% by mass. The tin reduction step includes a step of reducing the tin compound during the tin compound mixing step or after the tin compound mixing step, and an alkali-soluble tin salt or acid-soluble tin salt as the tin compound. Is used.

The nickel powder slurry is not particularly limited as long as it has a substantially spherical particle shape and nickel powder having an average particle diameter of 0.03 μm to 0.5 μm is dispersed in a solvent. For example, not only nickel powder obtained by a wet method but also nickel powder obtained by a vapor phase method such as a chemical vapor deposition method (CVD method) or a plasma method may be dispersed in a solvent. Furthermore, a slurry as an intermediate product produced in the course of the nickel powder production process by the wet method or the vapor phase method (for example, a nickel powder-containing slurry that is slurried with pure water to wash and remove water-soluble impurities (described later) Or an alkaline reaction final solution containing nickel crystallization powder), or a nickel powder-containing slurry prepared for wet classification for removing coarse particles.
As the solvent for the nickel powder slurry, it is not impossible to use a solvent such as an organic alcohol solvent such as ethanol. However, in consideration of workability, safety, and cost, an aqueous solvent (pure water, alkali or acid) is used. And the like are most preferable.

  According to the surface treatment method of the nickel powder according to the present invention with tin, the nickel powder of any of the wet method and vapor phase method is made into the above nickel powder slurry, and then the tin compound is added to the solvent in the nickel powder slurry. If it is dissolved and the tin compound is reduced, a nickel powder whose surface is treated with tin can be obtained.

  Here, in the surface treatment method using tin according to the present invention, the content of tin with respect to nickel is less than 1.5% by mass, preferably less than 1.0% by mass, and more preferably less than 0.5% by mass. Since the tin content is small compared to the case of solid solution, the tin layer for modifying (coating) the surface of the nickel particles is extremely thin, and the average particle size before and after the surface treatment with tin is substantially the same. You can think about it.

  If necessary, the nickel powder may be subjected to a sulfur coating treatment with a sulfur compound such as a mercapto compound or a disulfide compound so that the sulfur content of the nickel powder is 0.15% by mass or less simultaneously with the surface treatment with tin. Or before and after.

(2-1. Procedure of surface treatment step with tin)
As a specific procedure of the surface treatment process with tin, for example, nickel powder having a substantially spherical particle shape and an average particle diameter of 0.03 μm to 0.5 μm manufactured by a wet method or a gas phase method is used. The nickel powder slurry obtained by dispersing in a solvent containing water as a main component has a tin content of less than 1.5% by mass with respect to nickel (in the nickel powder surface-treated with the finally obtained tin), It is preferably mixed with an alkali-soluble or acid-soluble tin salt or an aqueous solution thereof (tin compound mixing step) so as to be less than 1.0% by mass, more preferably less than 0.5% by mass, and this alkali-soluble or acid-soluble. There is a step of reducing the tin salt to metal tin (tin reduction step) and modifying (coating) the surface of the nickel particles with tin. Reduction of the alkali-soluble or acid-soluble tin salt may be carried out by adding a reducing agent such as hydrazine after the tin compound mixing step, or replacing nickel particles with nickel and tin compound without using a reducing agent such as hydrazine. You may carry out by reaction.

  In addition to the above alkali-soluble and acid-soluble tin salts, a metal compound other than tin such as silver, bismuth, indium, antimony and zinc is added in a small amount so that the surface of the nickel particles is a metal other than tin and a small amount of tin. Nickel powders modified with components can also be produced.

  After completion of the surface treatment step, nickel powder surface-treated with tin can be obtained by separating from the nickel powder slurry using a known procedure, washing as necessary, and drying.

(2-2. Tin compounds used in the surface treatment step with tin)
The tin compound used in the present invention is an alkali-soluble tin salt or an acid-soluble tin salt.
As the alkali-soluble tin salt, a tin oxoacid salt can be used. The tin oxoacid salt is an alkali metal stannate (X ₂ SnO ₃ , where X = NH ₄ , Li, Na, K, Rb, Cs, which is a compound of Sn (IV). Among them, sodium stannate or potassium stannate is more preferable because it has high solubility in water, is inexpensive and easily available. The solution containing the alkali metal stannate is prepared by adding a tin inorganic acid salt or a tin organic acid salt, which will be described later, to the alkaline solution and neutralizing and hydrolyzing with an alkali component once to form tin hydroxide (Sn ( It is also possible to obtain by OH) ₄ ) and then reacting with an alkali component in the solution to dissolve it.

  Alkali metal stannate is soluble in alkaline nickel powder slurry, and has the effect of forming an alkaline solution even when added to and dissolved in neutral nickel powder slurry. Become. When the alkali metal stannate is reduced using hydrazine as a reducing agent in the alkaline nickel powder slurry, the hydrazine becomes stronger as the alkalinity becomes stronger, as described later. There is an advantage that the surface of the nickel particles can be modified (coating) by easily reducing the metal stannate to tin.

Examples of the acid-soluble tin salt include an inorganic acid salt of tin and an organic acid salt of tin.
As the inorganic acid salt, tin chloride (SnCl ₂ , SnCl ₂ .2H ₂ O, SnCl ₄ , or SnCl ₄ .5H ₂ O), tin nitrate (Sn (II)), which is a compound of Sn (II) or Sn (IV). NO ₃ ) ₂ , or Sn (NO ₃ ) ₄ ), tin sulfate (SnSO ₄ , or Sn (SO ₄ ) ₂ ), chlorostannic acid or its salt (X ₂ SnCl ₄ , or X ₂ SnCl ₆ , where X = H, NH ₄ , Li, Na, K, Rb, or Cs), and tin organic acid salts such as tin methanesulfonate or tin phenolsulfonate can be used. However, it is not limited to these. Among them, tin chloride (SnCl ₂ , SnCl ₂ .2H ₂ O, SnCl ₄ .5H ₂ O), tin sulfate (SnSO ₄ , Sn (SO ₄ ) ₂ ), hexachlorotin salt ((NH ₄ ) ₂ SnCl ₄ , K ₂ SnCl ₄ ) is preferable because it has high solubility in water, is inexpensive and easily available.

The acid-soluble tin salt is soluble in an acidic nickel powder slurry, and has an action of forming an acidic solution when added to and dissolved in a neutral nickel powder slurry. In any case, the nickel powder slurry becomes acidic. . In the reduction of the acid-soluble tin salt in the acidic nickel powder slurry, as described later, nickel particles may be used without using a reducing agent such as hydrazine (although a reducing agent may be used in combination). There is an advantage that the surface of the nickel particles can be modified (coating) by easily reducing the tin salt to tin by substitution reaction with nickel. This is because the nickel powder slurry is acidic, so nickel (Ni) of the nickel particles is easily dissolved and eluted in the slurry solvent as nickel ions (Ni ²⁺ ) and donates electrons to tin ions (Sn ⁴⁺ etc.) This is because the substitution reaction (reduction to Sn) can be promoted.

(2-3. Tin compound mixing step)
In the tin compound mixing step, a nickel powder slurry having a substantially spherical particle shape and an average particle diameter of 0.03 μm to 0.5 μm dispersed in a solvent is subjected to (surface by the finally obtained tin). The tin compound is added and mixed so that the amount of tin added to nickel (in the treated nickel powder) is less than 1.5 mass%, preferably less than 1.0 mass%, more preferably less than 0.5 mass%. It is a process. As the nickel powder to be surface-treated, those produced by a wet method or a vapor phase method can be used as described above. As a method for adding the tin compound to the nickel powder slurry, it is possible to add and mix the tin compound alone (solid, liquid) or as an aqueous solution in which the tin compound is dissolved in water. However, when an acid-soluble tin salt is added to and mixed with the acidic nickel powder slurry, the reduction reaction of the tin compound by the substitution reaction of the nickel particles in the acidic nickel powder slurry with nickel simultaneously with the addition of the acid-soluble tin salt Therefore, from the viewpoint of uniform surface treatment with tin, the addition time of the acid-soluble tin salt to the acidic nickel powder slurry is desirably shorter, preferably 10 seconds to 180 seconds, more preferably 20 seconds to 120 seconds, more preferably 30 to 80 seconds is preferable.

(2-4. Tin reduction process)
The tin reduction step is a step of reducing the aforementioned tin compound contained in the nickel powder slurry after the tin compound mixing step and subjecting the nickel particles to a surface treatment with tin. The tin reduction step may include a step of reducing the aforementioned alkali-soluble tin salt (alkali metal stannate) with a reducing agent such as hydrazine in an alkaline solution (in an alkaline nickel powder slurry) or in an acidic solution. A step of reducing the acid-soluble tin salt (such as tin chloride) with a reducing agent such as hydrazine in the acidic nickel powder slurry may be included.

  The tin reduction step may include a step of reducing the acid-soluble tin salt (such as tin chloride) in an acidic liquid (in an acidic nickel powder slurry) by a substitution reaction of nickel particles with nickel. The acid-soluble tin salt may be at least one of a tin inorganic acid salt and a tin organic acid salt.

The reducing agent used in the tin reduction step is not particularly limited, and examples thereof include hydrazine (N ₂ H ₄ , molecular weight: 32.05). Hydrazine includes hydrazine hydrate (N ₂ H ₄ .H ₂ O, molecular weight: 50.06), which is a hydrazine hydrate, in addition to anhydrous hydrazine, either of which may be used. The reduction reaction of hydrazine is as shown in formula (6), which will be described later. Particularly, it is alkaline and has a high reducing power, and the byproducts of the reduction reaction are nitrogen gas and water. They are characterized by the fact that they do not occur in the reaction solution, that there are few impurities in the hydrazine, and that they are easily available. Therefore, hydrazine is suitable as a reducing agent. For example, commercially available 60% by mass hydrazine hydrate can be used.

Here, the reduction reaction in the tin reduction step will be described. The reaction when the alkali-soluble alkali metal stannate ion (SnO ₃ ²⁻ ), which is a compound of Sn (IV), is reduced to tin (Sn) is a four-electron reaction of the following formula (1). is there.

The reaction in the case where acid-soluble tin ions (Sn ²⁺ ) and tetrachlorostannate ions (SnCl ₄ ²⁻ ), which are Sn (II) compounds, are reduced to tin (Sn) is as follows. It is a two-electron reaction of Formula (2) and Formula (4), and acid-soluble tin ions (Sn ⁴⁺ ) and hexachlorostannate ions (SnCl ₆ ²⁻ ), which are Sn (IV) compounds, are reduced. The reaction in the case of becoming tin (Sn) is a four-electron reaction of the following formulas (3) and (5).

The reaction of hydrazine (N ₂ H ₄ ) is a four-electron reaction of the following formula (6).
For example, Sn (IV) as a tin compound, alkali metal stannate ion (SnO ₃ ²⁻ ), tin ion (Sn ⁴⁺ ), hexachlorostannate ion (SnCl ₆ ²⁻ ) is reduced with hydrazine The total reduction reaction is expressed by the following formula (7), formula (9), and formula (11), respectively, and stoichiometrically (as a theoretical value), based on 1 mol of tin (Sn). 1.0 mol of hydrazine (N ₂ H ₄ ) is required.
On the other hand, when tin ions (Sn ²⁺ ) and tetrachlorostannic acid ions (SnCl ₄ ²⁻ ), which are Sn (II) compounds as tin compounds, are reduced with hydrazine, the overall reduction reaction is represented by the following formula, respectively. (8) It is represented by the formula (10), and stoichiometrically (as a theoretical value), 0.5 mol of hydrazine (N ₂ H ₄ ) is required per 1 mol of tin (Sn).

Similarly, when tin ions (Sn ⁴⁺ ) and hexachlorostannate ions (SnCl ₆ ²⁻ ), which are Sn (IV) compounds as tin compounds, are reduced by substitution reaction of nickel particles with nickel (Ni). The overall reduction reaction of each is represented by the following formulas (13) and (15): stoichiometrically (as a theoretical value), with respect to 1 mol of tin (Sn), nickel (Ni) 2. 0 moles are required.

On the other hand, when tin ions (Sn ²⁺ ) and tetrachlorostannate ions (SnCl ₄ ²⁻ ), which are Sn (II) compounds as tin compounds, are reduced by a substitution reaction of nickel particles with nickel (Ni) The overall reduction reaction of each is represented by the following formula (12) and formula (14), respectively, and stoichiometrically (as a theoretical value), 1 mol of tin (Sn) and 1 mol of nickel (Ni). 0 moles are required.

<3. Method for producing nickel powder using wet method>
First, the manufacturing method of the nickel powder using the wet method which concerns on one Embodiment of this invention is demonstrated. A method for producing nickel powder using a wet method according to an embodiment of the present invention includes at least a water-soluble nickel salt, a salt of a metal nobler than nickel, a reducing agent (for example, hydrazine), and an alkali hydroxide as a pH adjuster. A crystallization step of crystallization of nickel by a reduction reaction with hydrazine or the like in a reaction solution obtained by mixing water and water to obtain an alkaline reaction final solution containing nickel crystallization powder. In addition, if necessary, an amine compound or a sulfide compound is added to the reaction solution and acts as a hydrazine autolysis inhibitor (amine compound, sulfide compound) and a reduction reaction accelerator (complexing agent) (amine compound). You may let them. Moreover, you may add the crushing process performed as needed as a post-processing process.

  The nickel crystallized powder contained in the alkaline reaction final solution obtained in the crystallization step can be separated from the alkaline reaction final solution using a known procedure after surface treatment with tin by the following procedure. For example, nickel powder surface-treated with tin can be obtained through the procedures of washing, solid-liquid separation, and drying. The above surface treatment with tin is performed by adding a predetermined amount of a tin compound such as sodium stannate to an alkaline reaction final solution containing nickel crystallized powder or a diluted / cleaning solution, and reducing the tin compound to metallic tin, This is a surface treatment for modifying the surface of nickel particles with tin.

  In addition, after the surface treatment with tin, if necessary, an extremely small amount of a sulfur compound is added to the alkaline reaction final solution containing nickel crystallized powder and the diluted / cleaning solution so that the content becomes 0.15% by mass or less. A surface treatment (sulfur coating treatment) for modifying the surface of nickel particles with a sulfur component may be applied. In addition, the obtained nickel powder can be subjected to a heat treatment at about 200 ° C. to 300 ° C. in, for example, an inert atmosphere or a reducing atmosphere to obtain a nickel powder. These tin surface treatment, sulfur coating treatment and heat treatment can control the debinding behavior at the internal electrode and the sintering behavior of nickel powder during the production of the above-mentioned multilayer ceramic capacitor, so it is very effective when used within the proper range. It is.

  Furthermore, if necessary, a pulverization step (post-treatment step) for pulverizing the nickel crystallization powder is added, and coarse particles due to the connection of nickel particles generated during the nickel particle generation process in the crystallization step, etc. It is preferable to obtain a nickel powder in which the reduction of the above is achieved.

  By performing such a crystallization step and a pulverization step as necessary, nickel powder having a substantially spherical particle shape and an average particle size of 0.03 μm to 0.5 μm can be obtained.

(3-1. Crystallization step)
In the crystallization process, a nickel salt (exactly nickel ion or nickel complex ion) is used in a reaction mixture in which at least a water-soluble nickel salt, a metal salt noble than nickel, a reducing agent, an alkali hydroxide, and water are mixed. ) Can be reduced by a reduction reaction using a reducing agent such as hydrazine. In the present invention, when hydrazine is used, an amine compound or a sulfide compound is mixed with this reaction solution as necessary, and the decomposition of hydrazine as a reducing agent is suppressed in the presence of the amine compound or sulfide compound. The nickel salt can also be reduced.

(3-1-1. Agent used in crystallization step)
In the crystallization process of the present invention, a nickel salt, a salt of a metal nobler than nickel, a reducing agent, an alkali hydroxide, and, if necessary, a reaction solution containing various agents such as an amine compound and a sulfide compound and water are used. ing. Water as a solvent is ultrapure water (conductivity: ≦ 0.06 μS / cm (micro Siemens per centimeter)), pure water (conductivity: conductivity) from the viewpoint of reducing the amount of impurities in the obtained nickel powder. ≦ 1 μS / cm) is preferable, and it is preferable to use pure water which is inexpensive and easily available.

(A) Nickel salt The nickel salt used in the present invention is not particularly limited as long as it is a nickel salt that is readily soluble in water, and at least one selected from nickel chloride, nickel sulfate, and nickel nitrate is used. Can do. Among these nickel salts, nickel chloride, nickel sulfate or a mixture thereof is more preferable.

(B) Metal salt noble than nickel Metal salt noble than nickel has a lower ionization tendency than nickel, and therefore is reduced before nickel when nickel is reduced and deposited. Therefore, when a salt of a metal nobler than nickel is contained in a nickel salt solution, when the nickel is reduced and precipitated, the metal nobler than nickel is reduced first and acts as a nucleating agent serving as an initial nucleus. The particle size can be easily controlled and refined in the nickel crystallized powder (nickel powder) obtained by grain growth of these initial nuclei.

  Metal salts that are noble than nickel may be metal salts that are water-soluble and have a lower ionization tendency than nickel, such as water-soluble copper salts, gold salts, silver salts, platinum salts, palladium salts, rhodium. Examples thereof include water-soluble noble metal salts such as salts and iridium salts. For example, copper sulfate as a water-soluble copper salt, silver nitrate as a water-soluble silver salt, palladium (II) sodium chloride, palladium (II) ammonium chloride, palladium (II) nitrate as a water-soluble palladium salt, Although palladium (II) sulfate etc. can be used, it is not limited to these.

As the metal salt noble than nickel, it is preferable to use the above-mentioned palladium salt because the particle size distribution is somewhat wider but the particle size of the resulting nickel powder can be more finely controlled. The ratio of palladium salt to nickel [mol ppm] (number of moles of palladium salt / number of moles of nickel × 10 ⁶ ) in the case of using palladium salt should be appropriately selected according to the desired number average particle diameter of nickel powder. Can do. For example, if the average particle diameter of nickel powder is set to 0.03 μm to 0.5 μm, the ratio of palladium salt to nickel is in the range of 0.2 mol ppm to 100 mol ppm, preferably 0.5 mol ppm. A range of ˜25 mol ppm is preferable. When the ratio is less than 0.2 mol ppm, the average particle diameter of the obtained nickel powder may exceed 0.5 μm. On the other hand, if this ratio exceeds 100 mol ppm, a large amount of expensive palladium salt is used, which may lead to an increase in the cost of the nickel powder.

(C) a reducing agent reducing agent used in the crystallization step of the present invention is not particularly limited but, as with tin reduction step described above, for example, hydrazine (N ₂ H _4, molecular weight: 32.05) is Can be mentioned. Hydrazine includes hydrazine hydrate (N ₂ H ₄ .H ₂ O, molecular weight: 50.06), which is a hydrazine hydrate, in addition to anhydrous hydrazine, either of which may be used. The reduction reaction of hydrazine is as shown in formula (2), which will be described later. In particular, since it is alkaline and has a high reducing power, and the by-products of the reduction reaction are nitrogen gas and water, impurity components due to the reduction reaction are reduced. They are characterized by the fact that they do not occur in the reaction solution, that there are few impurities in the hydrazine, and that they are easily available. Therefore, hydrazine is suitable as a reducing agent. For example, commercially available 60% by mass hydrazine hydrate can be used.

(D) Alkali hydroxide Since the reducing power of hydrazine increases as the alkalinity of the reaction solution increases as shown in formula (2) described later, in the present invention, alkali hydroxide is increased in alkalinity in the crystallization step. It can be used as a pH adjuster. The alkali hydroxide is not particularly limited, but it is preferable to use an alkali metal hydroxide from the viewpoint of availability and cost. Specifically, it is more preferable to use one or more selected from sodium hydroxide (NaOH) and potassium hydroxide (KOH).

  The blending amount of the alkali hydroxide is such that the pH of the reaction solution is 9.5 or more, preferably 10 or more, more preferably 10.5 or more at the reaction temperature so that the reducing power of hydrazine as a reducing agent is sufficiently increased. It is good to decide so that it becomes. When the pH of the reaction solution is, for example, about 25 ° C. and about 70 ° C., the higher temperature of 70 ° C. is somewhat smaller.

(E) Amine compound Since the amine compound of the present invention has the action of a hydrazine self-decomposition inhibitor, a reduction reaction accelerator, and a nickel-particle connection inhibitor as described above, it is necessary. It may be added to the reaction solution. The amine compound is a compound containing two or more functional groups selected from a primary amino group (—NH ₂ ) or a secondary amino group (—NH—) in the molecule. For example, at least one of an alkyleneamine or an alkyleneamine derivative can be used. As an example, it is preferable to use an amine compound having at least a structure of the following formula A in which a nitrogen atom of an amino group in the molecule is bonded via a carbon chain having 2 carbon atoms.

More specifically, as the alkylene amine, ethylenediamine (H ₂ NC ₂ H ₄ NH ₂ ), diethylene triamine (H ₂ NC ₂ H ₄ NHC ₂ H ₄ NH ₂ ), triethylenetetramine (H ₂ N (C ₂ H ₄₎ NH) ₂ C ₂ H ₄ NH ₂ ), tetraethylenepentamine (H ₂ N (C ₂ H ₄ NH) ₃ C ₂ H ₄ NH ₂ ), pentaethylenehexamine (H ₂ N (C ₂ H ₄ NH) ₄ One or more selected from C ₂ H ₄ NH ₂ ) and propylene diamine (CH ₃ CH (NH ₂ ) CH ₂ NH ₂ ) can be used. Moreover, as an alkyleneamine derivative, tris (2-aminoethyl) amine (N (C ₂ H ₄ NH ₂ ) ₃ ), N- (2-aminoethyl) ethanolamine (H ₂ NC ₂ H ₄ NHC ₂ H ₄ OH) ), Ethylenediamine-N, N′-diacetic acid (other names: ethylene-N, N′-diglycine, HOOCCH ₂ NHC ₂ H ₄ NHCH ₂ COOH), N, N′-diacetylethylenediamine (CH ₃ CONHC ₂ H ₄ NHCOCH) ₃ ) One or more selected from 1,2-cyclohexanediamine (H ₂ NC ₆ H ₁₀ NH ₂ ) can be used. These alkylene amines and alkylene amine derivatives are water-soluble. Among them, ethylene diamine and diethylene triamine are preferable because they are easily available and inexpensive.

The action of the amine compound as a reduction reaction accelerator is considered to be due to the action of a complexing agent that forms nickel complex ions by complexing nickel ions (Ni ²⁺ ) in the reaction solution. Moreover, and autolysis inhibitor of hydrazine, for acting as a connecting inhibitors among nickel particles, and the primary amino group (-NH ₂₎ and secondary amino groups in the amine compound molecules (-NH-) It is presumed that the action is expressed by the interaction with the surface of the nickel crystallized powder in the reaction solution.

  In addition, it is preferable that the alkylene amine or alkylene amine derivative which is an amine compound has a structure of the above formula A in which the nitrogen atom of the amino group in the molecule is bonded via a carbon chain having 2 carbon atoms. This is because the effect of suppressing the decomposition of hydrazine molecules is increased. For example, if the nitrogen atom of the amino group that strongly adsorbs to the nickel crystallized powder is bonded via a carbon chain having 3 or more carbon atoms, the carbon chain becomes longer and the movement of the carbon chain portion of the amine compound molecule is free. The degree (flexibility of the molecule) is thought to increase. As a result, the contact of hydrazine molecules with the nickel crystallized powder cannot be effectively prevented, and the number of hydrazine molecules that self-decomposes due to the catalytic activity of nickel increases, reducing the effect of suppressing hydrazine self-decomposition. It is done.

Actually, ethynediamine (H ₂ NC ₂ H ₄ NH ₂ ) or propylene diamine (other names: 1,2-diaminopropane, 1, ₂ ) in which the nitrogen atom of the amino group in the molecule is bonded via a carbon chain having 2 carbon atoms. Compared with 2-propanediamine) (CH ₃ CH (NH ₂ ) CH ₂ NH ₂ ), trimethylenediamine (also known as: 1) in which the nitrogen atom of the amino group in the molecule is bonded via a carbon chain having 3 carbon atoms. , 3-diaminopropane, 1,3-propanediamine) (H ₂ NC ₃ H ₆ NH ₂ ) has been confirmed to be inferior in the action of inhibiting hydrazine self-decomposition.

  Here, the ratio [mol%] of the amine compound and nickel in the reaction solution (mol number of amine compound / mol number of nickel) × 100) is preferably in the range of 0.01 mol% to 5 mol%, preferably The range of 0.03 mol% to 2 mol% is preferable. If the ratio is less than 0.01 mol%, the amount of the amine compound is too small, and each function as a hydrazine self-decomposition inhibitor, a reduction reaction accelerator, or a connection inhibitor between nickel particles may not be obtained. is there. On the other hand, if the above ratio exceeds 5 mol%, the amine compound may become too strong as a complexing agent to form nickel complex ions, resulting in abnormal particle growth of the nickel crystallized powder. There is a possibility that the characteristics of the nickel powder may be deteriorated such that the granularity and sphericity of the powder are lost and the shape is insignificant, or a large number of coarse particles are formed in which the nickel particles are connected to each other.

(F) Sulfide compound The sulfide compound used in the present invention is different from the amine compound described above, and when used alone, the action of suppressing the self-decomposition of hydrazine is not so great. However, when used in combination with the above amine compound, it has the action of a hydrazine self-decomposition inhibitor that can greatly enhance the action of hydrazine self-decomposition. Therefore, it is good to add to a reaction liquid as needed. Examples of the sulfide compound include compounds containing one or more sulfide groups (—S—) in the molecule. In addition to the action of the hydrazine self-decomposition inhibitor, the sulfide compound also has an action as a connection inhibitor between nickel particles. When used in combination with the amine compound, the nickel particles are connected to each other. The generation amount of coarse particles can be reduced more effectively.

As the sulfide compound, higher water solubility is desirable. Therefore, a carboxy group (—COOH), a hydroxyl group (—OH), an amino group (primary: —NH ₂ , secondary: —NH— is further included in the molecule. , Tertiary: any one of carboxy group-containing sulfide compound, hydroxyl group-containing sulfide compound and amino group-containing sulfide compound containing at least one of -N <), and a thiazole ring (C A thiazole ring-containing sulfide compound containing at least one ₃ H ₃ NS) is also applicable although it is not highly water-soluble. More specifically, L (or D, DL) -methionine (CH ₃ SC ₂ H ₄ CH (NH ₂ ) COOH), L (or D, DL) -ethionine (C ₂ H ₅ SC ₂ H _4). CH (NH ₂ ) COOH), N-acetyl-L (or D, DL) -methionine (CH ₃ SC ₂ H ₄ CH (NH (COCH ₃ )) COOH), lanthionine (other names: 3, 3′- Thiodialanine) (HOOCCH (NH ₂ ) CH ₂ SCH ₂ CH (NH ₂ ) COOH), thiodipropionic acid (other name: 3,3′-thiodipropionic acid) (HOOCC ₂ H ₄ SC ₂ H ₄ COOH), Thiodiglycolic acid (other names: 2,2′-thiodiglycolic acid, 2,2′-thiodiacetic acid, 2,2′-thiobisacetic acid, mercaptodiacetic acid) (HOOCCH ₂ SCH ₂ COOH), methionol (other Name: 3- _{Chiruchio-1-propanol) (CH 3 SC 3 H 6} OH), thiodiglycol (another name: 2,2'-thio _{diethanol) (HOC 2 H 5 SC 2} H 5 OH), thiomorpholine (C ₄ H ₉ NS), one or more selected from thiazole (C ₃ H ₃ NS) and benzothiazole (C ₇ H ₅ NS) are preferred. Among these, methionine and thiodiglycolic acid are preferable because they are excellent in the hydrazine self-degradation suppression assisting action, and are easily available and inexpensive.

  About the effect | action as a self-decomposition suppression inhibitor of hydrazine by the said sulfide compound, or a connection inhibitor of nickel particles, it can estimate as follows. That is, in the sulfide compound, the sulfide group (—S—) in the molecule is adsorbed on the nickel surface of the nickel particle by intermolecular force, but by itself, the nickel crystallized powder is covered like the amine compound molecule described above. The protective effect does not increase. On the other hand, when an amine compound and a sulfide compound are used in combination, when the amine compound molecule is strongly adsorbed on the surface of the nickel crystallized powder to cover and protect it, there may be a small area that cannot be completely covered by the amine compound molecule. However, it is more effective to prevent the contact between the hydrazine molecules in the reaction solution and the nickel crystallized powder. The coalescence can also be prevented more strongly, and the above action is manifested.

  Here, the ratio [mol%] of the above sulfide compound and nickel in the reaction solution (mol number of sulfide compound / mol number of nickel) × 100) is preferably in the range of 0.01 mol% to 5 mol%, preferably The range is 0.03 mol% to 2 mol%, more preferably 0.05 mol% to 1 mol%. When the ratio is less than 0.01 mol%, the amount of the sulfide compound is too small, and there is a possibility that the actions of the hydrazine self-decomposition inhibitor and the nickel particle-linking inhibitor may not be obtained. On the other hand, even if the ratio exceeds 5 mol%, the above-mentioned effects are not improved, so the amount of the sulfide compound used is merely increased, the drug cost increases, and at the same time, the organic component is added to the reaction solution. The amount of compounding increases and the chemical oxygen demand (COD) of the reaction waste liquid in the crystallization step increases, resulting in an increase in waste liquid treatment cost.

(G) Other contents In the reaction solution of the crystallization step, in addition to the above-described nickel salt, metal salt noble than nickel, reducing agent (hydrazine), alkali hydroxide, amine compound, dispersant, complex Various additives such as an agent and an antifoaming agent may be contained in a small amount. For example, if an appropriate amount of dispersant or complexing agent is used in an appropriate amount, the graininess (sphericity) and surface smoothness of the nickel crystallization powder can be improved, or coarse particles can be reduced. There is. In addition, if an appropriate amount of an antifoaming agent is used, it suppresses foaming in the crystallization process caused by nitrogen gas generated by the crystallization reaction (see formula (2) to formula (4) described later). Thus, for example, it is possible to prevent the aqueous solution from overflowing from the container. As the dispersant, a known substance can be used. For example, alanine (CH ₃ CH (COOH) NH ₂ ), glycine (H ₂ NCH ₂ COOH), triethanolamine (N (C ₂ H ₄ OH) ₃ ). ), Diethanolamine (also known as iminodiethanol) (NH (C ₂ H ₄ OH) ₂ ) and the like. As the complexing agent, known substances can be used, such as hydroxycarboxylic acid, carboxylic acid (organic acid containing at least one carboxyl group), hydroxycarboxylic acid salt or hydroxycarboxylic acid derivative, carboxylate salt or carboxylic acid. Examples of the acid derivative include tartaric acid, citric acid, malic acid, ascorbic acid, formic acid, acetic acid, pyruvic acid, and salts and derivatives thereof. Further, the antifoaming agent is not particularly limited as long as it has an excellent foam breaking property under alkaline conditions, and an oil-type or solvent-type silicone-based or non-silicone-based antifoaming agent can be used.

(3-1-2. Crystallization procedure)
In the crystallization step, at least a water-soluble nickel salt and a nickel salt solution in which a metal salt nobler than nickel is dissolved in water, a reducing agent solution in which a reducing agent (for example, hydrazine) is dissolved in water, and hydroxylation An alkali hydroxide solution in which an alkali is dissolved in water is prepared, and these are added and mixed to prepare a reaction solution. Then, by a reduction reaction, a crystallization reaction is performed in which nickel particles are crystallized in the reaction solution to obtain a nickel crystallized powder. In addition, the amine compound and sulfide compound to be added as necessary are added to and mixed with any of the above solutions or a mixture of them before preparing the reaction solution, or prepared after preparing the reaction solution. It can be added and mixed. In a room temperature environment, the reduction reaction is started when the reaction solution is prepared.

  Here, a specific crystallization procedure is obtained by previously mixing a reducing agent solution and an alkali hydroxide solution in a nickel salt solution containing a nickel salt that is a reduction target and a metal salt that is nobler than nickel. A procedure for preparing a reaction solution by adding a reducing agent (for example, hydrazine) and a reducing agent / alkali hydroxide solution containing an alkali hydroxide, and adding a reducing agent solution (for example, a hydrazine solution) to the nickel salt solution. There are two types of procedures for preparing a reaction solution by adding and mixing an alkali hydroxide solution to the resulting nickel salt / reducing agent solution. In the former, a reducing agent (for example, hydrazine), which has high alkalinity and increased reducing power by alkali hydroxide, is added to and mixed with a nickel salt solution containing the substance to be reduced, while in the latter, a reducing agent (for example, hydrazine) is added. There is a difference in that the reducing power is increased by adjusting (increasing) the pH with an alkali hydroxide after being previously mixed with a nickel salt solution containing a reduced product.

  In the former case (when a nickel salt solution and a reducing agent / alkali hydroxide solution are added and mixed), the temperature at the time when the reaction solution is prepared, that is, when the reduction reaction starts (hereinafter referred to as the reaction start temperature). Depending on the nickel salt solution (a solution containing a nickel salt and a metal salt nobler than nickel) and an alkali hydroxide with a reducing agent / alkali hydroxide solution that has increased alkalinity and increased reducing power. When the time required for addition mixing (hereinafter, sometimes referred to as raw material mixing time) becomes longer, the alkalinity increases locally in the addition and mixing region of the nickel salt solution and the reducing agent / alkali hydroxide solution from the middle of the addition mixing. As a result, the reducing power of hydrazine is increased, and nucleation is caused by a metal salt that is nobler than nickel, which is a nucleating agent. Therefore, as the end of the raw material mixing time is reached, the nucleation effect of the added nucleating agent is weakened, and the dependency of the nucleation on the raw material mixing time is increased, and the nickel crystallized powder is refined or a narrow particle size distribution is obtained Tend to be difficult. This tendency is more remarkable when an alkaline reducing agent / alkali hydroxide solution is added to and mixed with a weakly acidic nickel salt solution. Since the above tendency can be suppressed as the mixing time of the raw material is shorter, mixing for a short time is desirable, but considering the restrictions on mass production facilities, the mixing time of the raw material is preferably 10 seconds to 180 seconds, more preferably 20 seconds to 120 seconds, more preferably 30 seconds to 80 seconds.

  On the other hand, in the latter case (in the case of adding an alkali hydroxide solution to a nickel salt / reducing agent solution in which a nickel salt solution and a reducing agent solution are added and mixed), a nickel salt and a salt of a metal nobler than nickel are used. In the nickel salt / reducing agent solution containing the reducing agent, the reducing agent hydrazine is added and mixed in advance to obtain a uniform concentration. Therefore, the dependency of alkali hydroxide on the raw material mixing time of nucleation generated when adding and mixing an alkali hydroxide solution is not increased as in the former case, and the nickel crystallized powder is refined or a narrow particle size distribution is obtained. This makes it easy. However, for the same reason as in the former case, the mixing time of the alkali hydroxide solution is short, but considering the restrictions on the mass production equipment, the mixing time is preferably 10 seconds to 180 seconds. Preferably 20 seconds to 120 seconds, more preferably 30 seconds to 80 seconds.

  As for the addition and mixing of the amine compound and sulfide compound of the present invention, as described above, the procedure of mixing in the reaction solution in advance before the reaction solution is prepared, and the addition and mixing after the reaction solution is prepared and the reduction reaction is started. Two types of procedures are mentioned.

  In the former case (when premixed in the reaction solution before the reaction solution is prepared), an amine compound or sulfide compound is premixed in the reaction solution, so a metal salt (nucleating agent) that is precious than nickel There is an advantage that various actions of the amine compound and the sulfide compound are expressed from the start of the nucleation due to. On the other hand, interaction with the surface of nickel particles such as adsorption of amine compounds and sulfide compounds may be involved in nucleation and affect the particle size and particle size distribution of the resulting nickel crystallized powder.

  Conversely, in the latter case (when the reaction solution is prepared and added and mixed after the start of the reduction reaction), after passing through the very initial stage of the crystallization process in which nucleation occurs due to the nucleating agent, the amine compound or sulfide compound is added. Add to the reaction mixture. Therefore, although the action of the amine compound or sulfide compound described above is somewhat delayed, the participation of the amine compound or sulfide compound in the nucleation is eliminated, so that the particle size and particle size distribution of the obtained nickel crystallized powder are There is an advantage that they are less affected by the compounds and are easier to control. Here, the mixing time in the addition and mixing of the amine compound or sulfide compound in the reaction solution in this procedure may be added all at once within a few seconds, or may be added in portions or dropwise over about several minutes to 30 minutes. Good. As described above, the amine compound has an action as a reduction reaction accelerator (complexing agent). Therefore, the slow addition will cause the crystal growth to proceed slowly and the nickel crystallization powder to become highly crystalline, but the suppression of hydrazine self-degradation will also act gradually, reducing the effect of reducing hydrazine consumption. The mixing time may be appropriately determined while considering the balance between the two. The timing for adding and mixing the amine compound and sulfide compound in the former procedure can be appropriately selected by comprehensively judging according to the purpose.

  Addition and mixing of nickel salt solution and reducing agent / alkali hydroxide solution, addition and mixing of nickel salt solution and reducing agent solution, and addition and mixing of alkali hydroxide solution to nickel salt / reducing agent solution, while stirring the solution Mixing with stirring is preferred. When mixing with stirring is good, the non-uniformity decreases depending on the location of the nucleation, and the dependency of the nucleation on the raw material mixing time and alkali hydroxide mixing time as described above decreases. It is easy to refine the size and obtain a narrow particle size distribution. As a method of stirring and mixing, a known method may be used, and it is preferable to use a stirring blade from the viewpoint of control of stirring and mixing property and equipment cost.

(3-1-3. Reduction reaction)
In the crystallization step, nickel crystallized powder is obtained by reducing the nickel salt with hydrazine in the reaction solution in the presence of alkali hydroxide and a metal salt nobler than nickel. Further, if necessary, a reduction reaction can be carried out by significantly suppressing the self-decomposition of hydrazine by the action of a very small amount of a specific amine compound or sulfide compound.

First, the reduction reaction in the crystallization process will be described. The reaction in the case where nickel ions (Ni ²⁺ ) crystallize to become nickel (Ni) is a two-electron reaction of the following formula (16). The reaction of hydrazine (N ₂ H ₄ ) is a four-electron reaction represented by the following formula (6). For example, as described above, when nickel chloride (NiCl ₂ ) is used as the nickel salt and sodium hydroxide (NaOH) is used as the alkali hydroxide, the entire reduction reaction is represented by the following formula (17). Nickel hydroxide (Ni (OH) ₂ ) produced by the neutralization reaction between sodium hydroxide and sodium hydroxide is represented by a reaction in which hydrazine is reduced, and stoichiometrically (as a theoretical value), nickel (Ni) 1 0.5 mol of hydrazine (N ₂ H ₄ ) is required with respect to mol.

  Here, from the reduction reaction of hydrazine of formula (6), it can be seen that the stronger the alkalinity of hydrazine, the greater its reducing power. The alkali hydroxide is used as a pH adjuster that increases alkalinity, and has a function of promoting the reduction reaction of hydrazine.

  As described above, in the conventional crystallization process, the active surface of the nickel crystallization powder serves as a catalyst, the hydrazine self-decomposition reaction represented by the following formula (18) is promoted, and hydrazine as a reducing agent is reduced. There was a case where it was consumed in large quantities. Therefore, although depending on the crystallization conditions such as the reaction start temperature, for example, about 2 mol of hydrazine per 1 mol of nickel and about 4 times the theoretical value necessary for the above-described reduction are generally used. Furthermore, as shown in Formula (18), in the autolysis of hydrazine, a large amount of ammonia is by-produced, and ammonia is contained in a high concentration in the reaction solution, resulting in a nitrogen-containing waste solution. Thus, the use of an excessive amount of hydrazine, which is an expensive drug, and the generation of processing costs for the nitrogen-containing waste liquid are factors that increase the manufacturing cost of nickel powder (wet nickel powder) by a wet method.

  Therefore, in the method for producing nickel powder of the present invention, a very small amount of a specific amine compound or sulfide compound is added to the reaction solution to remarkably suppress the self-decomposition reaction of hydrazine and greatly increase the amount of expensive hydrazine used as a drug. It is preferable to reduce. The specific amine compound can suppress hydrazine self-decomposition. (I) The specific amine compound and sulfide compound molecules adsorb on the surface of the nickel crystallized powder in the reaction solution, and (II) Molecules of specific amine compounds and sulfide compounds that physically interfere with the contact between the active surface of the powder and hydrazine molecules, act on the surface of the nickel crystal powder and impair the catalytic activity of the surface. It may be activated.

Conventionally, in the crystallization process by the wet method, nickel ions (Ni ²⁺ ) and complex ions such as tartaric acid and citric acid are used to reduce the reduction reaction time (crystallization reaction time) to a practical range. In general, a complexing agent that forms ionic nickel to increase the concentration of ionic nickel is used as a reduction reaction accelerator. However, these complexing agents such as tartaric acid and citric acid form coarse particles produced by the action of hydrazine self-decomposition inhibitors such as the specific amine compounds and sulfide compounds described above, or by connecting nickel particles together during crystallization. It does not have an effect as a connection inhibitor that makes it difficult to do.

  On the other hand, the specific amine compound has the advantage of acting as a complexing agent in the same manner as tartaric acid and citric acid, and has the functions of a hydrazine self-decomposition inhibitor, a linking inhibitor, and a reduction reaction accelerator. Yes.

(3-1-4. Reaction start temperature)
The crystallization reaction in the crystallization step is, for example, a solution containing a reducing agent (for example, hydrazine) and an alkali hydroxide (reduction) in a solution containing at least a water-soluble nickel salt or a salt of a metal nobler than nickel (nickel salt solution). The reaction is started in a reaction mixture in which an agent and an alkali hydroxide solution are added and mixed. In this case, the reaction start temperature of the crystallization reaction is preferably 40 ° C to 95 ° C, more preferably 50 ° C to 80 ° C, and further preferably 60 ° C to 70 ° C. The temperatures of the nickel salt solution and the reducing agent / alkali hydroxide solution are not particularly limited as long as the temperature of the mixture obtained by premixing them, that is, the reaction start temperature falls within the above temperature range, and can be freely set. Can be set.

  The higher the reaction start temperature, the more the reduction reaction is promoted and the nickel crystallized powder tends to be highly crystallized. On the other hand, the hydrazine self-decomposition reaction is further promoted. As the consumption increases, foaming of the reaction solution tends to become intense. Therefore, if the reaction start temperature is too high, the hydrazine consumption may increase significantly or the crystallization reaction may not be continued with a large amount of foaming. On the other hand, if the reaction start temperature is too low, the crystallinity of the nickel crystallized powder is remarkably reduced, or the reduction reaction is delayed and the time of the crystallizing process is greatly extended, resulting in a decrease in nickel powder productivity. Tend. For the above reasons, by setting the above temperature range, high-performance nickel powder can be produced at low cost while maintaining high productivity while suppressing hydrazine consumption.

(3-2. Surface treatment step with tin in wet method)
As shown in FIGS. 3 and 4, the surface treatment step with tin in the production process of nickel powder using a wet method is an alkaline reaction final solution (nickel powder slurry) containing nickel crystallized powder produced by a reduction reaction with hydrazine. In addition, the surface treatment with tin is performed on the nickel crystallized powder in the nickel powder slurry by the surface treatment step with tin, which includes an alkali reduction step (implemented as necessary), a tin compound mixing step, a tin reduction step, and the like. Then, the nickel crystallized powder surface-treated with tin is washed as necessary, solid-liquid separated using a known procedure, and dried to obtain nickel powder surface-treated with tin. Can do.
The details are as described in the above-mentioned items of “1. Nickel powder” or “2. Surface treatment method of nickel powder with tin”, and description thereof is omitted.

(3-2-1. Procedure of surface treatment step with tin in wet method)
Specific examples of the surface treatment step with tin in the manufacturing process of nickel powder using a wet method include, for example, an alkaline reaction final solution containing nickel crystallization powder and a nickel powder slurry that is a diluted / cleaning solution (crystallization step). A nickel powder slurry mainly composed of a later alkaline reaction final solution) and a tin content with respect to nickel (in the nickel powder surface-treated with the finally obtained tin) of less than 1.5% by mass, preferably 1. An alkali-soluble or acid-soluble tin salt or an aqueous solution thereof is mixed (tin compound mixing step) so as to be less than 0% by mass, more preferably less than 0.5% by mass, and this alkali-soluble or acid-soluble tin salt is converted into a metal. A step of reducing to tin (tin reduction step) and modifying (coating) the surface of the nickel particles with tin is exemplified. The reduction of the alkali-soluble or acid-soluble tin salt may be carried out with a reducing agent such as hydrazine which is usually left in the reaction solution or its diluted / washed solution, and if necessary, such as hydrazine after the tin compound mixing step. An additional reducing agent may be added. More specifically, the nickel crystallized powder produced by the reduction reaction with hydrazine is in the state of particles crystallized in the alkaline reaction final solution after the reduction reaction, and the alkaline reaction finished product containing the nickel crystallized powder is obtained. After the liquid or the diluted / cleaning liquid is made into a nickel powder slurry in which the nickel crystallized powder is uniformly dispersed by stirring or the like, the nickel crystallized powder is subjected to a surface treatment with tin.
The details are as described in the above-mentioned items of “1. Nickel powder” or “2. Surface treatment method of nickel powder with tin”, and description thereof is omitted.

(3-2-2. Tin compounds used in the surface treatment step with tin in the wet method)
The details of the tin compound used in the surface treatment step with tin in the production process of nickel powder using the wet method are as described in the above-mentioned item of “2. Surface treatment method with tin of nickel powder”. Description is omitted.

  When the tin compound is an alkali-soluble tin salt (alkali metal stannate), it is soluble in an alkaline reaction final solution (nickel powder slurry) containing nickel crystallized powder obtained in the crystallization process, so that the crystallization process The nickel crystallized powder can be directly added to the subsequent alkaline reaction final solution and subjected to a surface treatment with tin. In addition, when the reducing agent (hydrazine) remains in the alkaline reaction final solution, There is an advantage that the reducing agent can be effectively used by using it for the reduction reaction of the tin compound.

(3-2-3. Tin compound mixing step in wet method)
In the tin compound mixing process in the manufacturing process of nickel powder using a wet method, the nickel powder slurry which is the alkaline reaction final solution obtained in the crystallization process or its diluted / cleaning liquid (liquid obtained in the alkali reduction process described later) In addition, the content of tin with respect to nickel (in the nickel powder surface-treated with tin finally obtained) is less than 1.5% by mass, preferably less than 1.0% by mass, more preferably less than 0.5% by mass In this step, an alkali-soluble or acid-soluble tin salt or an aqueous solution thereof is mixed.

When the tin compound is an alkali-soluble tin salt (alkali metal stannate), the nickel crystallized powder is added directly to the alkaline reaction final solution (nickel powder slurry) containing the nickel crystallized powder obtained in the crystallization process. Can be subjected to a surface treatment with tin. Further, when the tin compound is an acid-soluble tin salt (such as tin chloride), the alkaline reaction final solution containing nickel crystallized powder obtained in the crystallization step is diluted and washed in the alkali reduction step described later to obtain an alkali. The component can be removed or reduced, and if necessary, the nickel crystallized powder can be surface-treated with tin by directly adding it to a slurry (nickel powder slurry) added with acid.
The details are as described in the item of “2. Surface treatment method of nickel powder with tin”, and the description thereof is omitted.

(3-2-4. Tin reduction step in wet method)
The tin reduction step in the manufacturing process of nickel powder using the wet method is to reduce the tin compound to metallic tin during the tin compound mixing step in the wet method or after the tin compound mixing step, and modify the surface of the nickel powder with tin (Coating). The tin reduction step may include a step of reducing the alkali-soluble tin salt with a reducing agent in an alkaline solution, or may include a step of reducing the acid-soluble tin salt with an reducing agent in an acidic solution. Furthermore, a step of reducing the acid-soluble tin salt by a substitution reaction of nickel particles with nickel in an acidic solution may be included. In addition, the reduction | restoration of the tin compound in the said tin compound mixing process means the reduction | restoration performed by the substitution reaction with the said nickel which starts a reduction reaction immediately after the addition start of the tin compound to a nickel powder slurry.
The details are as described in the item of “2. Surface treatment method of nickel powder with tin”, and the description thereof is omitted.

(3-2-5. Alkali reduction step in wet method)
The alkali reduction step in the nickel powder production process using the wet method is a step of obtaining a nickel powder slurry from which alkaline components have been removed or reduced from the alkaline reaction final solution containing the nickel crystallization powder obtained in the crystallization step. As described above, when an acid-soluble tin salt (such as tin chloride) is used as the tin compound, it is necessary to make the acid liquid when the tin compound is added to the nickel powder slurry. There is a risk that tin hydroxide (Sn (OH) _4, etc.) may precipitate due to neutralization and hydrolysis of the nickel, and for this purpose, the nickel powder slurry before adding the tin compound is at least weakly alkaline or neutral (preferably It must be made slightly acidic). Therefore, the alkali reduction step in the wet method is basically a step required when an acid-soluble tin salt (such as tin chloride) is used as the tin compound.

  A specific method for removing or reducing the alkaline component from the alkaline reaction final solution is, for example, removing the alkaline solution portion as a solvent from the alkaline reaction final solution by solid-liquid separation such as filtration or decantation to obtain pure water. Is added to reslurry to obtain a diluted / cleaning solution, and other general-purpose cleaning methods can be applied.

  As described above, the nickel powder surface-treated with tin by separating the nickel crystallized powder surface-treated with tin from the nickel powder slurry, washing and drying in the process of producing the nickel powder using the wet method. Can be obtained. Specific methods for separating the nickel crystallized powder surface-treated with tin from the nickel powder slurry include a method of separating using a Denver filter, a filter press, a centrifuge, a decanter, and the like. For example, the nickel crystallized powder is solid-liquid separated from the reaction solution after the surface treatment with tin, and sufficiently washed with high-purity water such as pure water (conductivity: ≦ 1 μS / cm), an air dryer, Drying at 50 to 300 ° C., preferably 80 to 150 ° C. using a general-purpose drying apparatus such as a hot air dryer, an inert gas atmosphere dryer and a vacuum dryer, to obtain nickel powder surface-treated with tin Can do. In addition, when drying at about 200 ° C. to 300 ° C. in an inert atmosphere, a reducing atmosphere, or a vacuum atmosphere using a drying apparatus such as an inert gas atmosphere dryer or a vacuum dryer, heat treatment is performed in addition to simple drying. It is possible to obtain nickel powder that has been surface-treated with tin subjected to.

(3-3. Crushing step (post-processing step))
The nickel crystallization powder (nickel powder) surface-treated with tin obtained in the crystallization step and the surface treatment step with tin, as described above, when an amine compound or a sulfide compound is added as necessary Since they act as a nickel particle linking inhibitor during the crystallization of nickel, the content ratio of coarse particles formed by linking nickel particles to each other in the process of reduction precipitation is not so large in the first place. However, depending on the crystallization procedure and crystallization conditions, the content ratio of coarse particles may become somewhat large, which may be a problem. In this case, a pulverization step is provided following the crystallization step, and nickel particles The coarse particles connected to each other can be divided at the connecting portion to reduce the coarse particles. In the crushing process, apply dry crushing methods such as spiral jet crushing and counter jet mill crushing, wet crushing methods such as high-pressure fluid impact crushing, and other general-purpose crushing methods. Is possible.

  EXAMPLES Hereinafter, although this invention is demonstrated further more concretely using an Example, this invention is not limited to a following example at all. As the characteristics of nickel powder, the average particle size, impurity content (oxygen content, chlorine content, alkali metal content), sulfur content, tin content, and resin decomposition peak temperature were evaluated as follows. ing.

(Average particle size)
The nickel powder obtained in the present invention has a substantially spherical particle shape, but the average particle diameter is an observation image using a scanning electron microscope (SEM, manufactured by JEOL Ltd., JSM-7100F) of nickel powder ( (SEM image) is the number average particle size obtained from the result of image analysis.

(Impurity content (oxygen content, chlorine content, alkali metal content))
With respect to the obtained nickel powder, the content of oxygen as impurities caused by surface oxidation of nickel particles, chlorine as impurities attributed to nickel chloride as a nickel raw material, and sodium as impurities attributed to sodium hydroxide were measured. Oxygen was measured using an oxygen analyzer by an inert gas melting method (LECO Corporation, TC436), and sodium was measured using an atomic absorption analyzer (manufactured by Hitachi High-Tech Science Co., Ltd., Z-5310).

(Sulfur content)
The obtained nickel powder was analyzed for sulfur content by the combustion method based on the sulfur content thought to be attributed to the sulfur compound such as a hydrazine self-decomposition inhibitor, or the sulfur compound treating agent such as mercapto compound. It measured using the apparatus (the product made by LECO Corporation, CS600).

(Tin content)
About the obtained nickel powder, content of tin was measured using the high frequency inductively coupled plasma (ICP) emission-spectral-analysis apparatus (Agilent Technology company make, 5100).

(Resin decomposition peak temperature)
Thermogravimetric measurement (TG) by heating a mixed powder in which 20 parts by weight of the obtained nickel powder and 1 part by weight of ethyl cellulose (EC) resin powder were uniformly mixed in a nitrogen atmosphere at a heating rate of 10 ° C./min. The resin decomposition behavior was evaluated. First, in the profile of mass change (ΔTG) with respect to temperature (FIG. 5), the temperature showing the minimum value that is the maximum value of mass change is determined as the resin decomposition peak temperature (Tn). ) Also for the resin powder alone, the temperature showing the minimum value that is the maximum value of the mass change amount was determined as the resin decomposition peak temperature (Tr), and the difference (Tr-Tn) was used as an index of the resin decomposition suppression effect. The resin decomposition peak temperature (Tr) of the ethyl cellulose resin powder alone measured under the above conditions was 340 ° C.

Example 1
[Preparation of solutions of nickel salts and salts of metals more precious than nickel]
405 g of nickel chloride hexahydrate (NiCl ₂ .6H ₂ O, molecular weight: 237.69) as a nickel salt, and one sulfide group (—S—) in the molecule as a sulfide compound as a self-degradation inhibitor 1.271 g of L-methionine (CH ₃ SC ₂ H ₄ CH (NH ₂ ) COOH, molecular weight: 149.21), palladium (II) ammonium chloride (also known as tetrachloropalladium (II) as a metal salt noble than nickel ) Ammonium acid) ((NH ₄ ) ₂ PdCl ₄ , molecular weight: 284.31) 0.040 mg dissolved in 1880 mL of pure water, nickel salt, sulfide compound, and metal of noble metal than nickel as main components A nickel salt solution that is an aqueous solution containing a nucleating agent that is a salt was prepared. Here, in the nickel salt solution, L-methionine which is a sulfide compound is a very small amount of 0.5 mol% (0.005 in molar ratio) with respect to nickel, and palladium is 0.08 mol ppm (0.15 with respect to nickel). Mass ppm).

[Preparation of reducing agent solution]
Commercially available industrial grade 60% hydrated hydrazine (MC Otsuka Chemical Co., Ltd.) diluted with pure water 1.97 times with hydrazine hydrate (N ₂ H ₄ · H ₂ O, molecular weight: 50.06) as a reducing agent 207 g) was weighed to prepare a reducing agent solution that was an aqueous solution containing no hydrazine as a main component and not containing alkali hydroxide. The molar ratio of hydrazine to nickel contained in the reducing agent solution was 1.46.

[Alkali hydroxide solution]
As an alkali hydroxide, 276 g of sodium hydroxide (NaOH, molecular weight: 40.0) was dissolved in 672 mL of pure water to prepare an alkali hydroxide solution that is an aqueous solution containing sodium hydroxide as a main component. The molar ratio of sodium hydroxide to nickel contained in the alkali hydroxide solution was 6.90.

[Amine compound solution]
As an amine compound as a self-decomposition inhibitor and a reduction reaction accelerator (complexing agent), ethylenediamine (abbreviation: EDA) (H) is an alkyleneamine containing two primary amino groups (—NH ₂ ) in the molecule. ₂ NC ₂ H ₄ NH ₂ , molecular weight: 60.1) 1.024 g was dissolved in 19 mL of pure water to prepare an amine compound solution that was an aqueous solution containing ethylenediamine as a main component. Ethylenediamine contained in the amine compound solution was a very small amount of 1.0 mol% (0.01 by mole) with respect to nickel.

  The materials used in the nickel salt solution, the reducing agent solution, the alkali hydroxide solution, and the amine compound solution, except for 60% hydrazine hydrate, were all reagents manufactured by Wako Pure Chemical Industries, Ltd.

[Tin surface treatment solution]
As a tin compound, 0.831 g of sodium stannate (Na ₂ SnO ₃ .3H ₂ O, molecular weight: 266.73) was dissolved in 50 mL of pure water to prepare a tin surface treatment solution containing sodium stannate as a main component. . Here, in the tin surface treatment solution, sodium stannate is 0.183 mol% (mol: 0.00183) with respect to nickel, and tin is 0.370 mass% with respect to nickel.

[Crystalling process]
A nickel salt solution in which nickel chloride and palladium salt are dissolved in pure water is placed in a Teflon (registered trademark) -coated stainless steel container equipped with a stirring blade and heated with stirring to a liquid temperature of 85 ° C. The above reducing agent solution containing hydrazine and water was added and mixed at a mixing time of 20 seconds to obtain a nickel salt / reducing agent-containing solution. To this nickel salt / reducing agent-containing solution, the alkali hydroxide solution containing alkali hydroxide and water at a liquid temperature of 25 ° C. was added and mixed at a mixing time of 80 seconds, and the reaction liquid (nickel chloride + palladium salt + Hydrazine + sodium hydroxide) was prepared and a reduction reaction (crystallization reaction) was started. The reaction start temperature was 63 ° C. The amine compound solution is added dropwise to the reaction solution over 10 minutes from 8 minutes to 18 minutes after the start of the reaction, and the reduction reaction proceeds while suppressing self-decomposition of hydrazine, whereby nickel particles are crystallized in the reaction solution. And nickel crystallization powder was obtained. Within 60 minutes from the start of the reaction, the reduction reaction of the above-described formula (17) was completed, the supernatant of the reaction solution was transparent, and it was confirmed that all nickel components in the reaction solution were reduced to metallic nickel. .

[Surface treatment process with tin]
The alkaline reaction final solution containing the nickel crystallized powder is in the form of a slurry. The nickel powder slurry is stirred, the tin surface treatment solution is added thereto, and stannic acid is added by the hydrazine remaining in the nickel powder slurry. The ions (SnO ₃ ²⁻ ) were reduced to metallic tin (Sn), and the nickel particles were subjected to a surface treatment with tin. After the surface treatment, using pure water with a conductivity of 1 μS / cm, the filtrate filtered from the nickel powder slurry is filtered and washed until the conductivity of the filtrate is 10 μS / cm or less, separated into solid and liquid, and then heated to 150 ° C. It dried in the set vacuum dryer, and obtained the nickel powder surface-treated with the tin.

  Based on 207 g of 60% hydrazine hydrate blended in the reducing agent solution, the amount of 60% hydrazine hydrate consumed in the crystallization reaction was 141 g, and the molar ratio to nickel was 0.97. Here, since the molar ratio of hydrazine consumed in the reduction reaction to nickel is assumed to be 0.5 from the above-described equation (17), the molar ratio of hydrazine consumed in the autolysis to nickel is 0.49. It is estimated that there was.

[Crushing treatment process (post-treatment process)]
Following the crystallization step, a pulverization step was performed to reduce coarse particles formed mainly by connecting nickel particles in the nickel powder. Specifically, the nickel powder surface-treated with the tin obtained in the crystallization step was subjected to a spiral jet crushing process which is a dry crushing method. The nickel powder surface-treated with the tin which concerns on Example 1 produced using the wet method according to the above process was obtained.

(Physical properties of nickel powder)
The average particle diameter of the obtained nickel powder was 0.24 μm. The contents in the nickel powder were 0.24% by mass for tin, 0.89% by mass for oxygen, <0.001% by mass for chlorine, 0.002% by mass for sodium, and 0.09% by mass for sulfur. It was. The resin decomposition peak temperature (Tn) of the nickel powder was measured and found to be 325 ° C. Therefore, (Tr-Tn) was 15 ° C.

(Example 2)
[Tin surface treatment solution]
0.221 g of sodium stannate (Na ₂ SnO ₃ .3H ₂ O, molecular weight: 266.73) as a tin compound was dissolved in 50 mL of pure water to prepare a tin surface treatment solution containing sodium stannate as a main component. . Here, in the tin surface treatment solution, sodium stannate is 0.049 mol% with respect to nickel, and tin is 0.098 mass% with respect to nickel.

  A nickel powder surface-treated with tin was obtained in the same manner as in Example 1 except that the tin surface treatment solution was used.

  The nickel powder surface-treated with the above tin was subjected to the same spiral jet crushing treatment as in Example 1. The nickel powder surface-treated with the tin which concerns on Example 2 produced using the wet method according to the above process was obtained.

(Physical properties of nickel powder)
The average particle diameter of the obtained nickel powder was 0.24 μm. The contents in the nickel powder were 0.09 mass% for tin, 0.80 mass% for oxygen, <0.001 mass% for chlorine, 0.002 mass% for sodium and 0.09 mass% for sulfur. It was. The resin decomposition peak temperature (Tn) of the nickel powder was measured and found to be 305 ° C. Therefore, (Tr-Tn) was 35 ° C.

(Example 3)
[Tin surface treatment solution]
1.79 g of sodium stannate (Na ₂ SnO ₃ .3H ₂ O, molecular weight: 266.73) as a tin compound was dissolved in 50 mL of pure water to prepare a tin surface treatment solution containing sodium stannate as a main component. . Here, in the tin surface treatment solution, sodium stannate is 0.394 mol% with respect to nickel, and tin is 0.796 mass% with respect to nickel.

  A nickel powder surface-treated with tin was obtained in the same manner as in Example 1 except that the tin surface treatment solution was used.

  The nickel powder surface-treated with the above tin was subjected to the same spiral jet crushing treatment as in Example 1. The nickel powder surface-treated with the tin which concerns on Example 3 produced using the wet method according to the above process was obtained.

(Physical properties of nickel powder)
The average particle diameter of the obtained nickel powder was 0.22 μm. The contents in the nickel powder were 0.41% by mass for tin, 0.86% by mass for oxygen, <0.001% by mass for chlorine, 0.002% by mass for sodium, and 0.09% by mass for sulfur. It was. The resin decomposition peak temperature (Tn) of the nickel powder was measured and found to be 335 ° C. Therefore, (Tr-Tn) was 5 ° C. FIG. 6 shows a photograph of the nickel powder of Example 3 observed by SEM. Not only the nickel powder of Example 3, but also the nickel powders of Examples 1, 2, and 4 each had a substantially spherical particle shape.

Example 4
[Preparation of solutions of nickel salts and salts of metals more precious than nickel]
405 g of nickel chloride hexahydrate (NiCl ₂ .6H ₂ O, molecular weight: 237.69) as a nickel salt, palladium (II) ammonium chloride (also known as: tetrachloropalladium (II) acid as a metal salt more precious than nickel 1.60 mg (ammonium) ((NH ₄ ) ₂ PdCl ₄ , molecular weight: 284.31) is dissolved in 1880 mL of pure water, and a nickel salt as a main component and a nucleating agent that is a metal salt of a metal more precious than nickel. A nickel salt solution which is an aqueous solution containing was prepared. Here, in a nickel salt solution, palladium is 6.0 mass ppm (3.3 mol ppm) with respect to nickel.

[Preparation of reducing agent solution]
Commercially available industrial grade 60% hydrated hydrazine (MC Otsuka Chemical Co., Ltd.) diluted with pure water 1.97 times with hydrazine hydrate (N ₂ H ₄ · H ₂ O, molecular weight: 50.06) as a reducing agent 276 g) was weighed to prepare a reducing agent solution that was an aqueous solution that did not contain alkali hydroxide and contained hydrazine as a main component. The molar ratio of hydrazine to nickel contained in the reducing agent solution was 1.94.

[Alkali hydroxide solution]
As an alkali hydroxide, 230 g of sodium hydroxide (NaOH, molecular weight: 40.0) was dissolved in 560 mL of pure water to prepare an alkali hydroxide solution that is an aqueous solution containing sodium hydroxide as a main component. The molar ratio of sodium hydroxide to nickel contained in the alkali hydroxide solution was 5.75.

[Amine compound solution]
As an amine compound, ethylenediamine (abbreviation: EDA) (H ₂ NC ₂ H ₄ NH ₂ , molecular weight: 60.1), which is an alkylene amine containing two primary amino groups (—NH ₂ ) in the molecule. 024 g was dissolved in 18 mL of pure water to prepare an amine compound solution that was an aqueous solution containing ethylenediamine as a main component. Ethylenediamine contained in the amine compound solution was a very small amount of 1.0 mol% (0.01 by mole) with respect to nickel.

[Tin surface treatment solution]
3.15 g of sodium stannate (Na ₂ SnO ₃ .3H ₂ O, molecular weight: 266.73) as a tin compound was dissolved in 50 mL of pure water to prepare a tin surface treatment solution containing sodium stannate as a main component. . Here, in the tin surface treatment solution, sodium stannate is 0.69 mol% (0.0069 in molar ratio) with respect to nickel, and tin is 1.40 mass% with respect to nickel.

[Crystalling process]
A nickel salt solution in which nickel chloride and palladium salt are dissolved in pure water is placed in a Teflon (registered trademark) -coated stainless steel container with stirring blades and heated while stirring to a liquid temperature of 75 ° C., and then hydrazine having a liquid temperature of 25 ° C. The above reducing agent solution containing water and water was added and mixed in a mixing time of 20 seconds to obtain a nickel salt / reducing agent-containing solution. To this nickel salt / reducing agent-containing solution, the alkali hydroxide solution containing alkali hydroxide and water at a liquid temperature of 25 ° C. was added and mixed in a mixing time of 80 seconds, and the reaction liquid (nickel chloride + palladium salt + Hydrazine + sodium hydroxide) was prepared and a reduction reaction (crystallization reaction) was started. The reaction start temperature was 63 ° C. The amine compound solution is added dropwise to the reaction solution over 10 minutes from 8 minutes to 18 minutes after the start of the reaction, and the reduction reaction proceeds while suppressing the self-decomposition of hydrazine to crystallize nickel particles in the reaction solution. Nickel crystallized powder was obtained. Within 60 minutes from the start of the reaction, the reduction reaction of the formula (17) was completed, the supernatant of the reaction solution was transparent, and it was confirmed that all nickel components in the reaction solution were reduced to metallic nickel.

[Surface treatment process with tin]
The alkaline reaction final solution containing the nickel crystallized powder is in the form of a slurry. The nickel powder slurry is stirred, the tin surface treatment solution is added thereto, and hydrazine as a reducing agent is added to the nickel powder slurry. The mixture was mixed to reduce stannate ions (SnO ₃ ²⁻ ) to metallic tin (Sn), and the nickel particles were subjected to a surface treatment with tin. Except this, it carried out similarly to Example 1, and obtained the nickel powder surface-treated with tin.

  The nickel powder surface-treated with tin was subjected to the same spiral jet crushing treatment as in Example 1. The nickel powder surface-treated with the tin which concerns on Example 4 produced using the wet method according to the above process was obtained.

(Physical properties of nickel powder)
The average particle diameter of the obtained nickel powder was 0.26 μm. The content in the nickel powder was 0.99% by mass for tin, 0.70% by mass for oxygen, 0.002% by mass for chlorine, 0.003% by mass for sodium, and 0.09% by mass for sulfur. . The resin decomposition peak temperature (Tn) of the nickel powder was measured and found to be 335 ° C. Therefore, (Tr-Tn) was 5 ° C.

(Example 5)
[Tin surface treatment solution]
A tin surface treatment solution containing sodium stannate as a main component was prepared by dissolving 6.30 g of sodium stannate (Na ₂ SnO ₃ .3H ₂ O, molecular weight: 266.73) as a tin compound in 100 mL of pure water. . Here, in the tin surface treatment solution, sodium stannate is 1.39 mol% (0.0139 in molar ratio) with respect to nickel, and tin is 2.80 mass% with respect to nickel.

  A nickel powder surface-treated with tin was obtained in the same manner as in Example 4 except that the tin surface treatment solution was used.

  The nickel powder surface-treated with the above tin was subjected to the same spiral jet crushing treatment as in Example 1. The nickel powder surface-treated with the tin which concerns on Example 5 produced using the wet method according to the above process was obtained.

(Physical properties of nickel powder)
The average particle diameter of the obtained nickel powder was 0.26 μm. The contents in the nickel powder were 0.12% by mass for tin, 0.75% by mass for oxygen, 0.002% by mass for chlorine, 0.003% by mass for sodium, and 0.09% by mass for sulfur. . The resin decomposition peak temperature (Tn) of the nickel powder was measured and found to be 335 ° C. Therefore, (Tr-Tn) was 5 ° C.

(Example 6)
[Tin surface treatment solution]
A tin surface treatment solution containing ammonium hexachlorotinate as a main component is prepared by dissolving 4.95 g of ammonium hexachlorostannate ((NH ₄ ) ₂ SnCl ₆ , molecular weight: 367.48) as a tin compound in 100 mL of pure water. did. Here, in the tin surface treatment solution, ammonium hexachlorostannate is 0.79 mol% with respect to nickel, and tin is 1.60 mass% with respect to nickel.

[Crystalling process]
The crystallization reaction was performed in the same manner as in Example 1 to obtain an alkaline reaction final solution containing nickel crystallization powder.
[Surface treatment process with tin]
Since this alkaline reaction final solution is strongly alkaline, when it is mixed as it is with the above tin surface treatment solution containing an acid-soluble tin salt, a precipitate of tin hydroxide (Sn (OH) ₄ ) is generated by neutralization and hydrolysis. In order to hinder the surface treatment with tin, prior to mixing with the tin surface treatment solution, the alkali component was removed from the alkaline reaction final solution as an alkali reduction step. Specifically, pure water having an electric conductivity of 1 μS / cm is used, and the alkaline reaction final solution is decanted and washed by dilution with pure water until the electric conductivity of the liquid becomes 10 μS / cm or less, and further, hydrochloric acid (HCl ) A small amount of the solution was added to obtain an acidic nickel powder slurry. After adding and mixing the above tin surface treatment solution to the above acidic nickel powder slurry to which the alkali component has been greatly removed in such an alkali reduction step and further adding a hydrochloric acid solution, hydrazine as a reducing agent is added and mixed. The nickel particles were then surface treated with tin. After the surface treatment with tin, the same treatment as in Example 1 was performed to obtain a nickel powder surface-treated with tin.

  The nickel powder surface-treated with the above tin was subjected to the same spiral jet crushing treatment as in Example 1. The nickel powder surface-treated with the tin which concerns on Example 6 produced using the wet method according to the above process was obtained.

(Physical properties of nickel powder)
The average particle diameter of the obtained nickel powder was 0.22 μm. The contents in the nickel powder were 0.89% by mass for tin, 0.93% by mass for oxygen, <0.001% by mass for chlorine, 0.002% by mass for sodium and 0.09% by mass for sulfur. It was. The resin decomposition peak temperature (Tn) of the nickel powder was measured and found to be 335 ° C. Therefore, (Tr-Tn) was 5 ° C.

(Example 7)
[Tin surface treatment solution]
A tin surface treatment solution containing 4.16 g of tin methanesulfonate ((CH ₃ SO ₃ ) ₂ Sn, molecular weight: 308.91) as a tin compound dissolved in 100 mL of pure water and containing tin methanesulfonate as a main component Prepared. Here, in the tin surface treatment solution, tin methanesulfonate is 0.79 mol% with respect to nickel, and tin is 1.60 mass% with respect to nickel.

[Crystalling process]
The crystallization reaction was performed in the same manner as in Example 1 to obtain an alkaline reaction final solution containing nickel crystallization powder.
[Surface treatment process with tin]
Since this alkaline reaction final solution is strongly alkaline, when it is mixed as it is with the above tin surface treatment solution containing an acid-soluble tin salt, a precipitate of tin hydroxide (Sn (OH) ₄ ) is generated by neutralization and hydrolysis. In order to hinder the surface treatment with tin, prior to mixing with the tin surface treatment solution, the alkali component was removed from the alkaline reaction final solution as an alkali reduction step. Specifically, pure water having an electrical conductivity of 1 μS / cm is used, and decantation of the alkaline reaction final solution and washing by dilution with pure water are performed until the electrical conductivity of the liquid becomes 10 μS / cm or less to obtain a nickel powder slurry. It was. The tin surface treatment solution was added to and mixed with the nickel powder slurry from which the alkali component was significantly removed in the alkali reduction step, and the nickel particles were subjected to a surface treatment with tin. In the surface treatment with tin, only the tin surface treatment solution is used, and hydrazine as a reducing agent is not added. Therefore, the reduction of the tin compound to metal tin (Sn) is performed by tin ions (Sn ⁴⁺ ). It is thought that it advanced by the substitution reaction of nickel and nickel (Ni). After the surface treatment with tin, the same treatment as in Example 1 was performed to obtain a nickel powder surface-treated with tin.

  The nickel powder surface-treated with tin was subjected to the same spiral jet crushing treatment as in Example 1. The nickel powder surface-treated with the tin which concerns on Example 7 produced using the wet method according to the above process was obtained.

(Physical properties of nickel powder)
The average particle diameter of the obtained nickel powder was 0.22 μm. The contents in the nickel powder were 0.75% by mass for tin, 0.97% by mass for oxygen, <0.001% by mass for chlorine, 0.002% by mass for sodium and 0.09% by mass for sulfur. It was. The resin decomposition peak temperature (Tn) of the nickel powder was measured and found to be 335 ° C. Therefore, (Tr-Tn) was 5 ° C.

(Comparative Example 1)
Nickel that was not surface-treated with tin in the same manner as in Example 4 except that the nickel crystallized powder was not surface-treated with tin in the nickel powder slurry (an alkaline reaction final solution containing nickel crystallized powder). A powder was obtained.

  The nickel powder not subjected to the surface treatment with tin was subjected to the same spiral jet crushing treatment as in Example 1. Through the above-described steps, a nickel powder that was manufactured using a wet method and was not surface-treated with tin according to Comparative Example 1 was obtained.

(Physical properties of nickel powder)
The average particle diameter of the obtained nickel powder was 0.26 μm. The resin decomposition peak temperature (Tn) of the nickel powder was measured and found to be 270 ° C. Therefore, (Tr-Tn) was 70 ° C. The content of nickel powder was below the detection limit for tin, 0.75% by mass for oxygen, 0.002% by mass for chlorine, 0.003% by mass for sodium, and sulfur for the content below the detection limit.

(Comparative Example 2)
Nickel that was not surface-treated with tin in the same manner as in Example 2 except that the nickel crystallized powder was not subjected to surface treatment with tin in the nickel powder slurry (an alkaline reaction final solution containing nickel crystallized powder). A powder was obtained.

  The nickel powder not subjected to the surface treatment with tin was subjected to the same spiral jet crushing treatment as in Example 1. Through the above-described steps, a nickel powder that was manufactured using a wet method and that was not surface-treated with tin according to Comparative Example 2 was obtained.

(Physical properties of nickel powder)
The average particle diameter of the obtained nickel powder was 0.24 μm. The content in the nickel powder was below detection limit for tin, 0.80% by mass for oxygen, <0.001% by mass for chlorine, 0.002% by mass for sodium, and 0.09% by mass for sulfur. The resin decomposition peak temperature (Tn) of the nickel powder was measured and found to be 285 ° C. Therefore, (Tr-Tn) was 55 ° C.

(Comparative Example 3)
In Comparative Example 3, in order to compare the physical properties of nickel powder (Examples 1 to 7) subjected to surface treatment with tin and conventional nickel powder subjected to sulfur coating treatment without performing surface treatment with tin, Carried out. Specifically, in nickel powder slurry (an alkaline reaction final solution containing nickel crystallized powder), nickel crystallized powder is not subjected to surface treatment with tin, and mercaptoacetic acid (thioglycolic acid) (HSCH ₂ COOH, molecular weight: 92). .12) was added in the same manner as in Example 2 except that the nickel crystallized powder was subjected to sulfur coating treatment to obtain nickel powder not subjected to surface treatment with tin.

  The nickel powder not subjected to the surface treatment with tin was subjected to the same spiral jet crushing treatment as in Example 1. Through the above-described steps, a nickel powder that was manufactured using a wet method and that was not surface-treated with tin according to Comparative Example 3 was obtained.

(Physical properties of nickel powder)
The average particle diameter of the obtained nickel powder was 0.24 μm. The content of nickel powder was below the detection limit for tin, 0.75% by mass for oxygen, <0.001% by mass for chlorine, 0.002% by mass for sodium, and 0.18% by mass for sulfur. The resin decomposition peak temperature (Tn) of the nickel powder was measured and found to be 335 ° C. Therefore, (Tr-Tn) was 5 ° C.

  Table 1 shows the conditions of the surface treatment step with tin for Examples 1 to 7 and Comparative Examples 1 to 3, and the evaluation results of the characteristics of the nickel powder. Moreover, the result of having measured the resin decomposition | disassembly behavior of the mixed powder of the nickel powder and ethyl cellulose resin in Examples 1-5 and Comparative Examples 1-3 and the resin decomposition | disassembly behavior of the resin simple substance in FIG. 5 is shown. In FIG. 5, the resin decomposition behavior of Example 5 and Comparative Example 3 were almost the same, and the results were difficult to distinguish.

[Summary]
When Comparative Examples 2 having the same crystallization process and not surface-treated with tin were compared with Examples 1-3 and 6 and 7 subjected to surface treatment with tin, the surface with tin It can be seen that (Tr-Tn), which is a reduction amount of the resin decomposition temperature, is decreased by the treatment, and the decomposition of the resin is suppressed by the surface treatment with tin. Similarly, even when Comparative Example 1 in which the crystallization process is the same and the surface treatment with tin is not applied to the comparative examples 1 and 5 in which the surface treatment with tin is performed is compared, the decomposition of the resin is not It can also be seen that it is suppressed by the surface treatment. Moreover, although Examples 3-7 have little sulfur content (<0.01 mass%-0.09 mass%), sulfur content produced by the conventional method of sulfur addition (sulfur coat treatment) It can also be seen that the amount of decrease in the resin decomposition temperature is almost equivalent to that of Comparative Example 3 having a large amount of 0.18% by mass.

  As is clear from the above examples, according to the present invention, nickel powder that can exhibit the effect of suppressing the decomposition of the resin by the resin decomposition catalytic action of nickel with a smaller amount of tin addition as in the conventional sulfur addition effect. Obviously, a method for producing the same and a method for surface treatment of nickel powder can be provided. In particular, according to the present invention, it is possible to provide a method for producing nickel powder by a wet method that can more easily and easily produce nickel powder that has been surface-treated with a small amount of tin.

Claims (16)

Having a substantially spherical particle shape,
The average particle size is 0.03 μm to 0.5 μm,
Surface treatment with tin,
The tin content is less than 1.5% by weight,
Nickel powder characterized by that. Resin decomposition peak temperature (Tr), which is a temperature indicating the maximum value of the mass change amount in the profile of the mass change amount with respect to the temperature, is measured by heating the ethyl cellulose resin in an inert atmosphere.
Resin decomposition peak temperature (Tn) which is the temperature which shows the maximum value of mass change in the profile of mass change with respect to temperature by measuring the resin decomposition temperature by heating the mixture of nickel powder and ethyl cellulose resin in an inert atmosphere Difference (Tr-Tn) is 40 ° C. or less,
The nickel powder according to claim 1. The tin content is less than 0.5% by weight,
The nickel powder according to claim 1 or 2, characterized by the above. Containing 0.15 mass% or less of sulfur,
The nickel powder according to any one of claims 1 to 3, wherein: A surface treatment method having a surface treatment step with tin, which obtains nickel powder surface-treated with tin having a substantially spherical particle shape and an average particle diameter of about 0.03 μm to 0.5 μm,
The surface treatment step with tin consists of a tin compound mixing step and a tin reduction step,
The tin compound mixing step includes a nickel powder slurry in which nickel powder having a substantially spherical particle shape and an average particle diameter of about 0.03 μm to 0.5 μm is dispersed in a solvent, and the amount of tin added to nickel is A step of mixing a tin compound to be less than 1.5% by mass,
The tin reduction step includes a step of reducing the tin compound during the tin compound mixing step or after the tin compound mixing step, and the tin compound is an alkali-soluble tin salt or an acid-soluble tin salt.
A method for surface treatment of nickel powder, characterized in that The tin reduction step includes a step of reducing the alkali-soluble tin salt with a reducing agent in an alkaline solution.
The nickel powder surface treatment method according to claim 5. The alkali-soluble tin salt is a tin oxoacid salt,
The nickel powder surface treatment method according to claim 5 or 6, wherein: The tin oxo acid salt is ammonium silver salt or alkali metal stannate (X ₂ SnO ₃ , where X = NH ₄ , Li, Na, K, Rb, Cs). is there,
The nickel powder surface treatment method according to claim 7. The tin reduction step is a step of reducing the acid-soluble tin salt by a substitution reaction with the nickel particles in an acidic solution, or reducing the acid-soluble tin salt with the nickel particles in an acidic solution. Including a step performed by a reducing agent separately from the reaction,
The nickel powder surface treatment method according to claim 5. The acid-soluble tin salt is at least one of a tin inorganic acid salt or a tin organic acid salt,
The method for surface treatment of nickel powder according to claim 5 or 9, wherein: The tin inorganic acid salt is tin chloride (SnCl ₂ or SnCl ₄ ), tin nitrate (Sn (NO ₃ ) ₂ , or Sn (NO ₃ ) ₄ ), tin sulfate (SnSO ₄ , or Sn (SO ₄ ). ₂ ), or at least one of chlorostannic acid or a salt thereof (X ₂ SnCl ₄ or X ₂ SnCl ₆ , where X = H 2, NH ₄ , Li, Na, K, Rb, or Cs) And
The tin organic acid salt is at least one of tin methanesulfonate and tin phenolsulfonate,
The nickel powder surface treatment method according to claim 10. The tin reduction step includes a step of reducing the tin compound with hydrazine;
The method for surface treatment of nickel powder according to any one of claims 5 to 11, wherein: A method for producing nickel powder surface-treated with tin having a substantially spherical particle shape and an average particle diameter of about 0.03 to 0.5 μm,
At least a water-soluble nickel salt, a salt of a metal nobler than nickel, a reducing agent, an alkali hydroxide and water are mixed to obtain a reaction solution, and then nickel particles are crystallized in the reaction solution by a reduction reaction. A crystallization step of obtaining an alkaline reaction final solution containing nickel crystallization powder,
It has a surface treatment process with tin consisting of a tin compound mixing process and a tin reduction process,
In the tin compound mixing step, a nickel powder slurry composed of an alkaline reaction final solution containing the nickel crystallized powder and an alkali-soluble tin salt are mixed so that the content of tin with respect to nickel is less than 1.5% by mass. Process
The tin reduction step includes a step of reducing the alkali-soluble tin salt in an alkaline liquid during the tin compound mixing step or after the tin compound mixing step.
A method for producing nickel powder, wherein A method for producing nickel powder surface-treated with tin having a substantially spherical particle shape and an average particle diameter of about 0.03 to 0.5 μm,
At least a water-soluble nickel salt, a salt of a metal nobler than nickel, a reducing agent, and an alkali hydroxide and water are mixed to obtain an alkaline reaction solution, and then nickel is crystallized in the alkaline reaction solution by a reduction reaction. A crystallization step of obtaining an alkaline reaction final solution containing nickel crystallization powder,
It has a surface treatment process with tin consisting of an alkali reduction process, a tin compound mixing process, and a tin reduction process,
The alkali reduction step is a step of obtaining a nickel powder slurry from which alkaline components have been removed or reduced from the alkaline reaction final solution,
The tin compound mixing step is a step of mixing an acid-soluble tin salt so that the content of tin with respect to nickel is less than 1.5% by mass, with the nickel powder slurry from which the alkali component has been removed or reduced,
The tin reduction step includes a step of reducing the acid-soluble tin salt during the tin compound mixing step or after the tin compound mixing step.
A method for producing nickel powder, wherein The tin reduction step includes a step of reducing the acid-soluble tin salt by a substitution reaction of nickel particles with nickel in an acidic solution.
The method for producing nickel powder according to claim 14. The tin reduction step includes a step of reducing the acid-soluble tin salt with a reducing agent separately from the substitution reaction of the nickel particles with nickel in an acidic solution.
The method for producing nickel powder according to claim 14.